Apparatus and method for determining an absolute pose of a manipulated object in a real three-dimensional environment with invariant features

ABSTRACT

An apparatus and method for optically inferring an absolute pose of a manipulated object in a real three-dimensional environment from on-board the object with the aid of an on-board optical measuring arrangement. At least one invariant feature located in the environment is used by the arrangement for inferring the absolute pose. The inferred absolute pose is expressed with absolute pose data (φ, θ, ψ, x, y, z) that represents Euler rotated object coordinates expressed in world coordinates (X o , Y o , Z o ) with respect to a reference location, such as, for example, the world origin. Other conventions for expressing absolute pose data in three-dimensional space and representing all six degrees of freedom (three translational degrees of freedom and three rotational degrees of freedom) are also supported. Irrespective of format, a processor prepares the absolute pose data and identifies a subset that may contain all or fewer than all absolute pose parameters. This subset is transmitted to an application via a communication link, where it is treated as input that allows a user of the manipulated object to interact with the application and its output.

RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 11/591,403 filed on Oct. 31, 2006 now U.S. Pat. No.7,729,515 and claiming priority from U.S. Provisional Patent ApplicationNo. 60/780,937 filed on Mar. 8, 2006, and further of U.S. patentapplication Ser. No. 10/769,484 filed on Jan. 30, 2004, all incorporatedherein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to determining an absolute poseof a manipulated object in a real three-dimensional environment withinvariant features, and it applies in particular to manipulated objectsused by human users to interface with the digital world.

BACKGROUND OF THE INVENTION

An object's pose in a real three-dimensional environment can beexpressed with respect to stationary references such as ground planes,reference surfaces, lines, solids, fixed points and other invariantfeatures disposed in the real three-dimensional environment. It isconvenient to parameterize the environment by a set of world coordinateswith a chosen reference point. The reference point may be the origin ofthe world coordinates, the center of a particularly prominent invariantfeature or the center of a distribution of two or more of thesefeatures. Once the locations and orientations of the invariant featuresdistributed in the environment are known, then knowledge of the spatialrelationship between the object and these invariant features enables oneto compute the object's pose.

An object's pose information combines the three linear displacementcoordinates (x, y, z) of any reference point on the object, as well asthe three inclination angles, also called the Euler angles (φ, θ, ψ)that describe the pitch, yaw and roll of the object. Conveniently, allparameters (x, y, z, φ, θ, ψ) are expressed in world coordinates toyield an absolute pose. In some cases, alternative expressions for theinclination angles such as rotations defined by the four Caylyle-Kleinangles or quaternions are more appropriate.

Determination of a sequence of an object's absolute poses at differenttimes allows one to compute and track the motion of the object in thereal three-dimensional environment. Over time, many useful coordinatesystems and method have been developed to track the pose of objects andto parametrize their equations of motion. For a theoretical backgroundthe reader is referred to textbooks on classical mechanics such asGoldstein et al., Classical Mechanics, 3^(rd) Edition, Addison Wesley2002.

Optical navigation is a particularly simple and precise way to trackmoving objects. The approach is also intuitive since our own humanvision system computes locations and motion trajectories of objects inreal three-dimensional environments. The precision of optical navigationis due to the very short wavelength of electromagnetic radiation incomparison with typical object dimensions, negligible latency in shortdistance measurements due to the extremely large speed of light as wellas relative immunity to interference. Thus, it is well known that theproblem of determining an absolute pose or a motion trajectory of anobject in almost any real three-dimensional environment may beeffectively addressed by the application of optical apparatus andmethods.

A particularly acute need for efficient, accurate and low-costdetermination of the absolute pose of an object in a realthree-dimensional environment is found in the field of hand-held objectsused for interfacing with the digital world. This field encompassesmyriads of manipulated objects such as pointers, wands, remote controls,gaming objects, jotting implements, surgical implements,three-dimensional digitizers and various types of human utensils whosemotion in real space is to be processed to derive a digital input for anapplication. In some realms, such application involves interactions thatwould greatly benefit from a rapid, low-cost method and apparatus forone-to-one motion mapping between real space and cyberspace.

Specific examples of cyberspace games played in three-dimensions (3-D)and requiring high-precision control object tracking involve scenarioswhere the manipulated control object is transported into or evenmimicked in cyberspace. Exemplary gaming objects of this variety includea golfing club, a racket, a guitar, a gun, a ball, a steering wheel, aflying control or any other accoutrement that the player wishes totransport into and utilize in a cyberspace application. A very thoroughsummary of such 3-D interfacing needs for graphics are found in U.S.Pat. No. 6,811,489 to Shimizu, et al.

A major problem encountered by state of the art manipulated objects suchas control wands and gaming implements is that they do not possess asufficiently robust and rapid absolute pose determination system. Infact, many do not even provide for absolute pose determination. Rather,they function much like quasi three-dimensional mice. These solutionsuse motion detection components that rely on optical flow sensors,inertial sensing devices or other relative motion capture systems toderive the signals for interfacing with cyberspace. In particular, manyof such interface devices try to solve just a subset of the motionchanges, e.g., inclination. An example of an inclination calculationapparatus is found in U.S. Pat. No. 7,379,841 to Ohta while a broaderattempt at determining relative motion is taught in U.S. Pat. No.7,424,388 to Sato and U.S. Application 2007/0049374 to Ikeda, et al.

Unfortunately, one-to-one motion mapping between space and cyberspace isnot possible without the ability to digitize the absolute pose of themanipulated object with respect to a well-defined reference location inreal space. All prior art devices that do not solve the full motionproblem, i.e., do not capture successive poses of the manipulated objectwith a method that accounts for all six degrees of freedom (namely, thevery parameters (x, y, z, φ, θ, ψ) inherent in three-dimensional space)encounter limitations. Among many others, these include informationloss, appearance of an offset, position aliasing, gradual drift andaccumulating position error.

In general, the prior art has recognized the need for tracking all sixdegrees of freedom of objects moving in three-dimensions. Thus, opticalnavigation typically employs several cameras to determine the positionor trajectory of an object in an environment by studying images of theobject in the environment. Such optical capturing or tracking systemsare commonly referred to as optical motion capture (MC) systems. Ingeneral, motion capture tends to be computationally expensive because ofsignificant image pre- and post-processing requirements, as well asadditional computation associated with segmentation and implementationof algorithms. One particular system taught by McSheery et al. in U.S.Pat. No. 6,324,296 discloses a distributed-processing motion capturesystem that employs a number of light point devices as markers, e.g.,infrared LEDs, attached to the object whose motion is to be determined.The markers use unique sequences of light pulses to represent theirunique identities and thus enable filtering out of information notbelonging to the markers (i.e., background noise) by the imaging cameraslocated in the environment. Since McSheery's system permits a great dealof irrelevant information from the imaging sensors (e.g., CCDs) to bediscarded before image processing, the system is less computationallyexpensive than more traditional motion capture systems.

Another three-dimensional position and orientation sensing system thatemploys markers on the object is taught by Kosaka et al. in U.S. Pat.No. 6,724,930. In this case the markers are uniquely identified based oncolor or a geometric characteristic of the markers in the extractedregions. The system uses an image acquisition unit or camera positionedin the environment and relies on image processing functions to removetexture and noise. Segmentation algorithms are used to extract markersfrom images and to determine the three-dimensional position andorientation of the object with respect to the image acquisitionapparatus.

Still another way of employing markers in position and orientationdetection is taught in U.S. Pat. No. 6,587,809 by Majoe. The object istracked by providing it with markers that are activated one at a timeand sensed by a number of individual sensors positioned in theenvironment. The position of the energized or active marker isdetermined by a control unit based on energy levels received by theindividual sensors from that marker.

The above approaches using markers on objects and cameras in theenvironment to recover object position, orientation or trajectory arestill too resource-intensive for low-cost and low-bandwidthapplications. This is due to the large bandwidth needed to transmitimage data captured by cameras, the computational cost to the hostcomputer associated with processing image data, and the data networkcomplexity due to the spatially complicated distribution of equipment(i.e., placement and coordination of several cameras in the environmentwith the central processing unit and overall system synchronization).

Despite the above-mentioned limitations of general motion trackingsystems, some aspects of these systems have been adapted in the field ofmanipulated objects used for interfacing with computers. Such objectsare moved by users in three-dimensions to produce input for computerapplications. Hence, they need to be tracked in all six degrees offreedom. Therefore, recent three-dimensional wands and controls do teachsolving for all six degrees of freedom.

For example, U.S. Patent Application 2008/0167818 to Kimber et al. has apassive wand with no on-board devices or LEDs. The wand is viewed frommultiple cameras finding the full 6 degrees of freedom to provide formore precise estimation of wand pose is expressly taught. Similarly,U.S. Pat. No. 6,982,697 to Wilson et al. teaches the use of externalcalibrated cameras to decode the orientation of the pointer used forcontrol actions. U.S. Patent Application 2006/0109245 to Wilson, et al.further teaches how intelligent computing environments can takeadvantage of a device that provides orientation data in relative motionmode and absolute mode. Further teachings on systems that use externalor not-on-board cameras to determine the pose and motion of a wand orcontrol and use it as input into various types of applications can befound in U.S. Patent Applications: 2008/0192007, 2008/0192070,2008/0204411, 2009/0164952 all by Wilson.

Still other notable teachings show as few as a single off-board camerafor detecting three-dimensional motion of a controller employed for gamecontrol purposes. Such cameras may be depth sensing. Examples ofcorresponding teachings are found in U.S. Patent Application2008/0096654 by Mondesir, et al., as well as U.S. Patent Applications2008/0100825, 2009/0122146 both by Zalewski, et al.

Unfortunately, approaches in which multiple cameras are set up atdifferent locations in the three-dimensional environment to enablestereo vision defy low-cost implementation. These solutions also requireextensive calibration and synchronization of the cameras. Meanwhile, theuse of expensive single cameras with depth sensing does not provide forrobust systems. The resolution of such systems tends to be lower thandesired, especially when the user is executing rapid and intricatemovements with the manipulated object in a confined or close-rangeenvironment.

Another approach involves determining the position or attitude of athree-dimensional object in the absolute sense and using it for agraphical user interface. One example of this approach is taught in U.S.Pat. No. 6,727,885 to Ishino, et al. Here the sensor is on-board themanipulated object. A projected image viewed by the sensor and generatedby a separate mechanism, i.e., a projection apparatus that imbues theprojected image with characteristic image points is employed to performthe computation. Additional information about such apparatus and itsapplication for games is found in U.S. Pat. No. 6,852,032 to Ishino andU.S. Pat. No. 6,993,206 to Ishino, et al.

The solution proposed by Ishino et al. is more versatile than the priorart solutions relying on hard-to-calibrate and synchronize multi-camerasystems or expensive cameras with depth sensing capabilities.Unfortunately, the complexity of additional hardware for projectingimages with characteristic image points is nontrivial. The same is trueof consequent calibration and interaction problems, including knowledgeof the exact location of the image in three-dimensional space. Thissolution is not applicable to close-range and/or confined environments,and especially environments with typical obstructions that interferewith line-of-sight conditions.

There are still other teachings attempting to improve on both theapparatus and method aspects of generating computer input withmanipulated objects such as wands, pointers, remote controls (e.g., TVcontrols). A very illuminating overall review of state of the arttechnologies that can be used for interacting with virtual environmentsand their limitations are discussed by Richard Halloway in “VirtualEnvironments: A Survey of the Technology”, University of North Carolinaat Chapel Hill, September 1993 (TR93-033). Still more recent teachingsfocusing on how absolute pose data can be used in specific contexts andfor remote control applications is discussed in the following U.S.Patent Applications: 2007/0189737; 2008/0106517; 2008/0121782;2008/0272272; 2008/0309511; 2009/0066647; 2009/0066648; 2009/0153389;2009/0153475; 2009/0153478; 2009/0158203 and 2009/0158222.

In sum, despite considerable amount of work in the field, a clear andpressing need for low-cost, robust and accurate apparatus for absolutemotion capture remains. Specifically, what is needed is an apparatusthat permits one to obtain absolute pose data from manipulated objectfor purposes of interacting with the digital world. Such apparatusshould not only be low-cost, robust and accurate, but it should also beconvenient and easy to use at high frame rates in close-range andconfined three-dimensional environments.

OBJECTS AND ADVANTAGES

It is the object of the present invention to introduce a particularlyeffective optical navigation apparatus and methods for opticallyinferring or measuring the absolute pose of objects manipulated in realthree-dimensional environments. More particularly, it is an objective ofthe present invention to address manipulated objects such as hand-helddevices moved directly by a human user in close-range, realthree-dimensional environments including constrained environments,living quarters and work-spaces. The numerous objects and advantages ofthe apparatus and method of invention will become apparent upon readingthe ensuing description in conjunction with the appended drawingfigures.

ABSTRACT OF THE DISCLOSURE

The objects and advantages of the present invention are accomplished byan optical apparatus and by an optical method that work with an absolutepose of a manipulated object. Specifically, the apparatus is designedfor processing absolute pose data derived from the absolute pose of themanipulated object that exists and moves in a real three-dimensionalenvironment. The apparatus has at least one invariant feature that isplaced in the real three-dimensional environment. An optical measuringarrangement is provided on-board the manipulated object for opticallyinferring the absolute pose from on-board the object using the one ormore invariant features. The inferred absolute pose is expressed withabsolute pose data (φ, θ, ψ, x, y, z) that represents Euler rotatedobject coordinates expressed in world coordinates (X_(o), Y_(o), Z_(o))with respect to a reference location. In other words, the apparatusworks with all six degrees of freedom (three translational degrees offreedom and three rotational degrees of freedom) available to objectsmoving in real three-dimensional space. Furthermore, the apparatus isequipped with a processor for preparing the absolute pose data andidentifying a subset of the absolute pose data. In the most generalcase, the subset may contain all absolute pose -data corresponding tothe complete absolute pose that was optically inferred. The apparatusemploys a communication link, such as a wireless communication link, fortransmitting the subset to an application.

The apparatus of invention may use any convenient location, whethercorresponding to the position of an actual item or entity in real spaceor not, as a reference location. Advantageously, the reference locationis selected to be a world origin (0, 0, 0) of the world coordinates(X_(o), Y_(o), Z_(o)). Furthermore, the one or more invariant featurespreferably include among them one or several high optical contrastfeatures. Indeed, it is even more preferable that the one or more highoptical contrast features be constituted by light sources. Suitablelight sources include, but are not limited to screens, display pixels,fiber optical waveguides and light-emitting diodes. Among the latter,infrared emitting diodes or IR LEDs are preferred. Alternatively, thehigh optical contrast feature or features can be reflectors orretro-reflectors.

In some embodiments the application has an output that is displayed to auser or users who may or may not be handling the manipulated object. Inthese embodiments the subset includes the input for interacting with theapplication's output. For example, in some embodiments the output hasone or more visual elements such as images, graphics, text or icons. Theapparatus has a display such as a display screen or a projection displayfor displaying the visual elements to the user. In one very specificembodiment, the display is a touch sensitive display that allows theuser to also interact with the output via touch and multi-touchgestures.

Alternatively or in addition, the same or different embodiments mayinclude audio elements in the application's output. These audio elementscan be tones, tunes, musical compositions and alert signals. Inembodiments where the output includes audio elements the apparatus hasspeakers for playing the audio elements to the user.

In some embodiments the optical measuring arrangement has alight-measuring component equipped with a lens and an optical sensor.For example, the lens can be an imaging lens for imaging thethree-dimensional environment and the optical sensor can be aphotodetector for sensing light arriving from the one or more invariantfeatures. Specifically, the photodetector can be a pixel array sensor,e.g., a CMOS, a CCD or a PIN-diode sensor. In cases where the apparatusemploys one or more predetermined light sources and these light sourcesact as beacons (i.e., they are distinguishable) the photodetector can bea position-sensing device (PSD) that directly determines a centroid oflight flux from the light source or sources. To avoid ambientillumination interference, it is preferable that the light sources beconstituted by a number of infrared emitting diodes or IR LEDs in suchembodiments. In addition, the IR LEDs can be modulated in a certainpattern to further improve their signal-to-noise performance and renderthem better distinguishable, i.e., improving their functioning asbeacons.

The optical measuring unit in other embodiments of the apparatus has anactive illumination component that projects a certain light into thereal three-dimensional environment. The active illumination componentreceives a scattered portion of the light from the one or more invariantfeatures and uses that scattered portion in its optical inference of theabsolute pose of the manipulated object. In some embodiments, the activeillumination component can comprise a scanning unit with a scanningmirror, i.e., a tiltable or rotatable mirror, which directs the lightinto the real three-dimensional environment. In this embodiment it isconvenient that the light be collimated in the form of a scanning lightbeam.

Whether the optical measuring arrangement has a component with a lensand an optical sensor or an active illumination component, it may befurther supplemented with an auxiliary motion detection component, e.g.,a relative motion detection component. Such auxiliary component mayinclude an inertial sensing device such as a gyroscope or anaccelerometer. Alternatively, this auxiliary motion detection componentmay include an optical flow measuring unit similar to those used by anoptical flying mouse. Still other auxiliary motion detection componentssuch as magnetic field measuring units or acoustic field measuring unitscan be employed in the apparatus of the present invention, asappropriate to perform the interpolation between times t_(i) whenabsolute pose is inferred optically by the optical measuringarrangement.

Depending on the application, the manipulated object can be any type ofobject that is routinely handled or otherwise used by humans for controlor interaction purposes. For example, the manipulated object can be apointer, a wand, a remote control, a three-dimensional mouse, a gamecontrol, a gaming object, a jotting implement, a surgical implement, athree-dimensional digitizer, a digitizing stylus or any other type ofutensil or tool employed by human beings for any productive purposewhatsoever. Among gaming objects, the specific object can be furthersubdivided among golfing clubs, tennis rackets, squash rackets, guitars,guns, knives, swords, spears, balls, clubs, bats, steering wheels,joysticks and flying controls.

A person skilled in the art will further realize that the applicationwill also dictate the appropriate selection of manipulated object. Inparticular, the application can be selected from the group consisting ofreality simulations such as flight training programs or military drills,remote control applications including remote surgery, cyber games,virtual worlds with and without avatars, searches for test and graphicsearch terms, photography applications including re-touching, audioapplications and augmented realities in both personal and commercialspheres of endeavor.

The method of invention calls for processing absolute pose data derivedfrom an absolute pose of a manipulated object. The steps involve placingthe manipulated object in a real three-dimensional environment that hasone or more invariant features and optically inferring the absolute posefrom on-board the manipulated object. The optical inference relies onthe one or more invariant features. The absolute pose is reported in theform of absolute pose data (φ, θ, ψ, x, y, z), which represent the Eulerrotated object coordinates expressed in world coordinates (X_(o), Y_(o),Z_(o)) with respect to a reference location. The steps further includepreparing the absolute pose data, identifying a subset of the absolutepose data, and transmitting the identified subset to an application.

For many applications it is important to obtain the full motion or someparameters of the motion of the manipulated object. In those embodimentsof the invention, the measuring is performed periodically at timest_(i), such that the sequence of absolute pose data at these differenttimes t_(i) describes the motion. Preferably, the motion is reported asa sequence of the optically inferred absolute poses, therefore yieldingabsolute motion in the real three-dimensional space with respect to thereference location, e.g., the world origin (0, 0, 0) or some otherconvenient reference location. For best signal-to-noise performance ofsuch absolute motion tracking or navigation it is recommended that theone or more invariant features include at least one light source andthat the light source be modulated.

In some embodiments the subset of the absolute pose data includes atleast one orientation parameter. That at least one orientationparameters can be used as input to the application. In other words, thecombination of yaw, pitch and roll are used as input, e.g., when theapplication is a three-dimensional geographical map and a point of viewfrom which to view the map needs to be entered by a user handing themanipulated object. In some cases, even one of these angles, e.g., asingle Euler angle, can be used as input.

In other cases, the subset of the absolute pose data includes at leastone position parameter. Again, that at least one position parameter canbe used as input to the application. For example, the position parameteris at least one Cartesian coordinate and preferably describes thelocation of a reference point on the manipulated object in worldcoordinates (X_(o), Y_(o), Z_(o)). The location of that reference pointis used as input, and in some cases just one Cartesian coordinate of thereference point can be used as that direct input parameter; e.g., thedisplacement along the z-axis can be used as an input for a zoomfunction of the application.

Many applications that simulate the real world and many gamingapplications in particular, may request subsets that include allabsolute pose data (φ, θ, ψ, x, y, z). This request may be necessary toperform one-to-one mapping between space and a cyberspace or virtualspace employed by the application.

Applications typically provide user output of some variety. In thoseapplications the subset of absolute pose data can allow the user tointeract with the output. For example, the supported interaction mayinclude, but is not limited to, text input, modification of the outputor re-arrangement of the output. Given that the output may include audioelements and visual elements, the interaction applies to either or bothof these types of output elements at the same time or sequentially.

The method of invention supports optically inferring the absolute posefrom on-board the manipulated object by receiving light from the one ormore invariant features by an optical measuring component equipped withan optical sensor and a lens. The method also supports optical inferencefrom on-board the manipulated object by projecting a certain light(e.g., structured light) into the real three-dimensional environmentcontaining the one or more invariant features and receiving a scatteredportion of the light from the one or more invariant features. In oneparticular instance, this approach may further include directing thelight into the real three-dimensional environment by scanning.

Furthermore, the method may include interpolating the absolute pose withan auxiliary motion detection component that may or may not measureabsolute pose or may not even measure all parameters of a relative pose.For example, the auxiliary motion detection component is an inertialsensing device and the interpolation is performed between times t_(i),or at times when the absolute pose is not being inferred optically.Alternatively, the auxiliary motion detection component is an opticalflow unit, e.g., a flying optical mouse unit, and the step ofinterpolating is again performed between times t_(i). Other suitableinterpolation techniques employ magnetic field measuring units oracoustic field measuring units.

The method can be applied with many different types of applicationsincluding ones in which the user is represented by an avatar that has atoken, e.g., a replica or other representation of the manipulated objectitself. The application may further superpose one or more virtualelements onto the real three-dimensional environment. The virtualelement or elements can be further rendered interactive with themanipulated object by the application, e.g., as may be the case in avirtual reality application. In these situations, the virtual elementmay contain data about one or more aspects of the real three-dimensionalenvironment. For example, the virtual element may be a description ofservices provided by a store existing in the real three-dimensionalenvironment and be superposed on that environment in the form anadvertisement to inform the user.

The specifics of the invention and enabling details are described belowwith reference to the appended drawing figures.

DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a three-dimensional view of an apparatus of the inventionillustrating the motion of a manipulated object.

FIG. 2A-C are diagrams illustrating the Euler rotation convention asused herein.

FIG. 3 is a block diagram illustrating the formatting or preparation ofthe absolute pose data into subsets.

FIG. 4 is a three-dimensional view of another apparatus according to theinvention.

FIG. 5 is a partial cut-away view showing the manipulated object of theapparatus of FIG. 4.

FIG. 6 is a diagram showing the processing of image data captured by theabsolute motion detection module on-board the manipulated object of FIG.5.

FIG. 7 is a three-dimensional diagram illustrating a preferred opticalapparatus for tracking a manipulated object according to the invention.

FIG. 8A is a graph illustrating the intensity of a typical ambientemission spectrum.

FIG. 8B is a graph illustrating a transmittance of an infrared filteremployed in the embodiment of FIG. 7.

FIG. 9 is a diagram with a top plan view of the surface of a centroidsensing device in the form of a position sensitive detector (PSD).

FIG. 10 is a flow diagram of an exemplary absolute pose and motioncapture program implemented by the apparatus of FIG. 7.

FIG. 11 is a top plan view of a position sensing device (PSD) withcircular symmetry for use in optical apparatus in accordance with thepresent invention.

FIG. 12 is a three-dimensional diagram of another optical apparatus fortracking a manipulated object and employing a PSD and beacons.

FIG. 13 is a three-dimensional diagram showing in more detail thedisplay and output generated by the application of the optical apparatusof FIG. 12.

FIG. 14 is a three-dimensional diagram of another apparatus in which themanipulated object is a hand-held tool.

FIG. 15 is a block diagram illustrating a few exemplary uses of commandand input data derived from a manipulated object in accordance with theinvention.

FIG. 16 is a three-dimensional diagram showing a manipulated objectusing an active illumination component with a tiltable scanning mirror.

FIG. 17 is a three-dimensional diagram showing another manipulatedobject that employs another type of active illumination component withrotating scan mirrors.

FIG. 18 is a three-dimensional diagram illustrating a manipulated objecthaving an auxiliary motion detection component with an inertial sensingdevice.

FIG. 19 is a three-dimensional diagram showing how an optical flowmeasuring unit serves as an auxiliary motion detection component.

FIG. 20A is a three-dimensional diagram illustrating how an on-boardoptical measuring arrangement for inferring absolute pose issupplemented by an auxiliary motion detection component using anelectronic magnetic sensing element.

FIG. 20B is a three-dimensional diagram illustrating how an on-boardoptical measuring arrangement for inferring absolute pose issupplemented by an auxiliary motion detection component using anacoustic sensor and acoustic sources.

FIG. 21 illustrates how the apparatus and method of invention areembodied in a cyber game.

FIG. 22 illustrates an apparatus in which the manipulated object is anaircraft and the three-dimensional environment is provided withstationary and moving sets of invariant features.

FIG. 23 shows an embodiment in which more than one manipulated object isconfigured to infer its absolute pose optically from on-board inaccordance with the invention.

FIG. 24 shows an embodiment in which the apparatus of invention isemployed with an augmented reality application.

DETAILLED DESCRIPTION

To appreciate the basic aspects of the present invention, we initiallyturn to a simple version of an apparatus 10 in accordance with theinvention, as shown in FIG. 1. Apparatus 10 has a manipulated object 14whose motion 40 in a real three-dimensional environment 18 is expressedby absolute pose data 12. Apparatus 10 processes absolute pose data 12that describe the absolute pose of manipulated object 14 at a number ofmeasurement times t_(i). Thus, successive pose data 12 collected at thechosen measurement times describe the motion that manipulated object 14executes or is made to execute by a user 38.

Manipulated object 14 is any object that is moved either directly orindirectly by a user 38 and whose pose when object 14 is stationary orin motion yields useful absolute pose data 12. For example, manipulatedobject 14 is a pointer, a wand, a remote control, a three-dimensionalmouse, a game control, a gaming object, a jotting implement, a surgicalimplement, a three-dimensional digitizer, a digitizing stylus ahand-held tool or any utensil. In fact, a person skilled in the art willrealize that a manipulated object 14 can be even be an entire devicesuch as a cell phone or a smart object that is handled by user 38 toproduce meaningful motion 40.

In the present case, manipulated object 14 is a pointer that executesmotion 40 as a result of a movement performed by the hand of a user 38.Pointer 14 has a tip 16 that will be used as a reference point fordescribing its absolute pose in real three-dimensional environment 18.In general, however, any point on object 14 can be selected as referencepoint 16, as appropriate or convenient.

Pointer 14 has an on-board optical measuring arrangement 22 foroptically inferring its absolute pose with the aid of one or moreinvariant features 32, 34, 36 disposed at different locations in realthree-dimensional environment 18. Invariant features 32, 34, 36 are highoptical contrast features such as edges of objects, special markings, orlight sources. In the present embodiment, invariant feature 32 is anedge of an object such as a table (object not shown), invariant feature34 is a special marking, namely a cross, and feature 36 is a lightsource. It is possible to use features 32, 34, 36 that are all locatedin a plane (coplanar) or else at arbitrary locations (non-coplanar)within real three-dimensional environment 18 as conveniently defined byglobal or world coordinates (X_(o), Y_(o), Z_(o)). The limitation isthat, depending on the type of features 32, 34, 36 a sufficient numberof them have to be visible to on-board optical measuring arrangement 22at measurement times t_(i), as described in more detail below.

In the present embodiment the world coordinates (X_(o), Y_(o), Z_(o))chosen to parameterize real three-dimensional environment 18 areCartesian. A person skilled in the art will recognize that other choicesincluding polar, cylindrical or still different coordinate systems canbe employed. In addition, it will be appreciated that features 32, 34,36 can be temporarily or permanently affixed at their spatial locationsas required for measuring the pose of pointer 14. Indeed, the spatiallocations of features 32, 34, 36 can be changed in an arbitrary manner,as long as on-board optical measuring arrangement 22 is appraised oftheir instantaneous spatial locations at times t_(i).

The spatial locations of features 32, 34, 36, whether temporary orpermanent, are conveniently expressed in world coordinates (X_(o),Y_(o), Z_(o)). Furthermore, if possible, the spatial locations offeatures 32, 34 and 36 are preferably such that at least a subset ofthem is visible to on-board optical measuring arrangement 22 in allabsolute poses that pointer 14 is expected to assume while undergoingmotion 40. Invariant features 32, 34, 36 are used in deriving a relativeor absolute position of tip 16 of pointer 14 in real three-dimensionalenvironment 18. Features 32, 34, 36 are also used for opticallyinferring the remaining portion of the absolute pose, i.e., theorientation of pointer 14.

A number of optical measurement methods using optical measuringarrangement 22 to infer the relative or absolute pose of pointer 14 canbe employed. In any of these methods, arrangement 22 uses one or moreon-board components to obtain pose data 12 in accordance with anywell-known absolute pose recovery technique including geometricinvariance, triangulation, ranging, path integration and motionanalysis. In some embodiments arrangement 22 has a light-measuringcomponent with a lens and an optical sensor that form an imaging system.In other embodiments arrangement 22 has an active illumination componentthat projects structured light or a scanning component that projects ascanning light beam into environment 18 and receives a scattered portionof the scanning light beam from features 32, 34. Specific examples ofthe various possible components will be explained in detail below.

Apparatus 10 has a processor 26 for preparing absolute pose data 12corresponding to absolute pose of pointer 14 and for identifying asubset 48 of absolute pose data 12 required by an application 28.Specifically, application 28 uses subset 48 which may contain all orless than all of absolute pose data 12. Note that processor 26 can belocated on pointer 14 or it can be remote, e.g., located in a remotehost device, as is the case in this embodiment.

A communication link 24 is provided for sending absolute pose data 12 toapplication 28. Preferably, communication link 24 is a wirelesscommunication link established with the aid of a wireless transmitter 30mounted on pointer 14. In embodiments where processor 26 and application28 are resident on pointer 14, communication link 24 can be a directelectrical connection. In still other embodiments, communication link 24can be a wired remote link.

During operation user 38 holds pointer 14 in hand and executes amovement such that pointer 14 executes motion 40 with respect toinvariant features 32, 34, 36 in world coordinates (X_(o), Y_(o), Z_(o))that parametrize real three-dimensional environment 18. For bettervisualization, motion 40 is indicated in dashed lines 42, 44 that markthe positions assumed by tip 16 and end 46 of pointer 14 during motion40. For the purposes of this invention, line 42 is referred to as thetrace of tip 16. In some specific applications of the present invention,trace 42 of tip 16 may be confined to a surface embedded in realthree-dimensional environment 18. Such surface can be plane, e.g., aplanar jotting surface, or it can be curved.

Motion 40 may produce no movement of end 46 or tip 16, i.e., no trace42. In fact, motion 40 is not limited by any parameter other than thoseof standard mechanics of rigid body motion known form classicalmechanics. Accordingly, changes in orientation of pointer 14 areconsidered to be motion 40. Likewise, changes in position of tip 16 (orany other reference point) in (x, y, z) coordinates convenientlyexpressed in world coordinates (X_(o), Y_(o), Z_(o)) are also consideredto be motion 40. In the present case, orientation of pointer 14 isdescribed by inclination angle θ, rotation angle φ and roll angle ψreferenced with respect to a center axis C.A. of pointer 14. A change inat least one of these angles constitutes motion 40.

In the present case, tip 16 moves along line 42 as pointer 14 isinclined with respect to a normal Z′ at inclination angle θ equal toθ_(o). For simplicity, normal Z′ is selected to be parallel to the Z_(o)axis of world coordinates (X_(o), Y_(o), Z_(o)) Furthermore, rotationand roll angles φ, ψ are equal to φ_(o), ψ_(o) respectively. Forconvenience, in this embodiment angles θ, φ and ψ are Euler angles. Ofcourse, other angles can be used to describe the orientation of pointer14. In fact, a person skilled in the art will appreciate that anyconvention for describing the rotations of pointer 16 can be adapted forthis description. For example, the four Carlyle-Klein angles, thedirection cosines, quaternions or still other descriptors of tilt, yawand roll can be employed in such alternative conventions.

FIGS. 2A-C illustrate a convention for describing the orientation ofpointer 14 using Euler angles θ, φ, ψ. Pointer 14 has a length lmeasured from tip 16 at the origin of non-rotated object coordinates(X′, Y′, Z′) as shown in FIG. 2A. Center axis C.A. is collinear with theZ′ axis, and it passes through tip 16 and the origin of non-rotatedobject coordinates (X′, Y′, Z′). In the passive rotation convention usedherein, object coordinates will be attached to pointer 14 while pointer14 is rotated from its initial upright position in which Z′ is parallelto Z_(o) of world coordinates (X_(o), Y_(o), Z_(o)).

Now, FIG. 2A illustrates a first counterclockwise rotation by firstEuler angle φ of object coordinates (X′, Y′, Z′) about the Z′ axis. Thisrotation of the object coordinates does not affect the Z′ axis so oncerotated Z″ axis is collinear with non-rotated Z′ axis (Z″=Z′). On theother hand, axes X′ and Y′ are rotated by first Euler angle φ to yieldonce rotated axes X″ and Y″.

FIG. 2B illustrates a second counterclockwise rotation by second Eulerangle θ applied to once rotated object coordinates (X″, Y″, Z″). Thissecond rotation is performed about the once rotated X″ axis andtherefore it does not affect the X″ axis (X′″=X″). On the other handaxes Y″ and Z″ are rotated by second Euler angle θ to yield twicerotated axes Y′″ and Z′″. This second rotation is performed in a plane Πcontaining once rotated axes Y″, Z″ and twice rotated axes Y′″, Z′″.Note that axis C.A. of pointer 14 is rotated counterclockwise by secondEuler angle θ in plane Π and remains collinear with twice rotated axisZ′″.

A third counterclockwise rotation by third Euler angle ψ is applied totwice rotated object coordinates (X′″, Y′″, Z′″) as shown in FIG. 1C.Rotation by ψ is performed about twice rotated axis Z′″ that is alreadycollinear with object axis Z rotated by all three Euler angles.Meanwhile, twice rotated axes X′″, Y′″ are rotated by ψ to yield objectaxes X,Y rotated by all three Euler angles. Object axes X, Y, Z rotatedby all three Euler angles φ, θ and ψ define Euler rotated objectcoordinates (X, Y, Z). Note that tip 16 of pointer 14 remains at theorigin of all object coordinates during the Euler rotations.

Now, referring back to FIG. 1, the absolute pose of pointer 14 includesits orientation, i.e., Euler angles (φ, θ, ψ), and position of tip 16,i.e., the coordinates (x, y, z) of tip 16 that was chosen as thereference point. The orientation of pointer 14 and position of tip 16are expressed in world coordinates (X_(o), Y_(o), Z_(o)). Worldcoordinates (X_(o), Y_(o), Z_(o)) have a reference location, in thiscase the world origin (0, 0, 0) that can be used to describe an absoluteposition of tip 16. In fact, world coordinates (X_(o), Y_(o), Z_(o)) canbe used for an absolute measure of any parameter(s) of the pose ofpointer 14. Alternatively, any parameter(s) of the pose of pointer 14can be described in a relative manner, e.g., with reference tonon-stationary or relative coordinates (X_(i), Y_(i), Z_(i)) or simplywith respect to the previous pose.

For the purposes of the present invention, it is important to be able tooptically infer, at least from time to time, the absolute pose ofpointer 14. To do this, one relates Euler rotated object coordinatesdescribing the orientation of pointer 14 to world coordinates (X_(o),Y_(o), Z_(o)) Note that the orientation of object axis Z′ in worldcoordinates (X_(o), Y_(o), Z_(o)) prior to the three Euler rotations isnormal to plane (X_(o), Y_(o)). Second Euler angle θ defines the onlycounterclockwise rotation of object coordinates that is not about anobject Z axis (this second rotation is about the X′=X′″ axis rather thanaxis Z′, Z″ or Z′″). Thus, Euler angle θ is an inclination angle θbetween the completely Euler rotated object axis Z or axis C.A. andoriginal object axis Z′, which is normal to plane (X_(o), Y_(o)).

Optical measuring arrangement 22 infers the absolute pose of pointer 14during motion 40 at measurement times t_(i) and processor 26 preparesthe corresponding absolute pose data 12. Note that absolute pose data 12consist of inferred values of parameters (φ, θ, ψ, x, y, z) atmeasurement times t_(i). Invariant features 32, 34, 36 are located atpositions that are defined in world coordinates (X_(o), Y_(o), Z_(o)).These positions stay fixed at least during measurement and usuallypermanently. Knowledge of the absolute positions of features 32, 34, 36in world coordinates (X_(o), Y_(o), Z_(o)) allows the optical measuringarrangement 22 to describe the absolute pose of pointer 14 with absolutepose data 12 expressed in parameters (φ, θ, ψ, x, y, z) at measurementtimes t_(i) in Euler rotated object coordinates within world coordinates(X_(o), Y_(o), Z_(o)). The expression of absolute pose data ispreferably with respect to a reference location such as world origin (0,0, 0) of world coordinates (X_(o), Y_(o), Z_(o)).

Of course, alternative locations within world coordinates can also bechosen as reference locations with respect to which the absolute pose ofpointer 14 is expressed. For example, the center of invariant feature 34may be chosen as the reference location and the locations of referencepoint 16 on pointer 14 at n measurement times t_(i) can be denoted bycorresponding n vectors D_(i), as shown in the drawing.

The frequency with which the absolute pose is inferred, i.e., the timest_(i), depends on the use of absolute pose data 12 corresponding to thatabsolute pose and the desired performance, e.g., temporal resolution. Itshould be noted that periodic optical inference of absolute pose is notlimited to any predetermined times t_(i) or frequency schedule. In otherwords, the times between any two successive optical inferences ormeasurements of the absolute pose can be arbitrary. Preferably, however,arrangement 22 infers the absolute pose at a frequency that is highenough to obtain absolute pose data 12 that describe motion 40 at thetemporal resolution required by application 28.

Wireless transmitter 30 of communication link 24 sends absolute posedata 12 here defined by parameters (φ, θ, ψ, x, y, z) collected atmeasurement times t_(i) to processor 26. Absolute pose data 12 can betransmitted continuously, in bursts, in parts, at arbitrary or presettimes or as otherwise desired. Processor 26 prepares a subset 48 ofabsolute pose data 12, for example the absolute position (x, y, z) oftip 16 and sends it to application 28. Application 28 uses absoluteposition (x, y, z) of tip 16 at measurement times t_(i) to chart trace42 of tip 16 as pointer 14 executes motion 40. In other words, unit 28recovers trace 42 corresponding to the movement of tip 16. Note that theresolution of trace 42 in absolute space can be improved by increasingthe sample of measurements of absolute trace points traversed inenvironment 18 by increasing the frequency of measurement times t_(i).

It should also be noted that pose data 12 should be formatted forappropriate communications between transmitter 30, processor 26 andapplication 28. Any suitable communication and formatting standards,e.g., IEEE interface standards, can be adapted for these purposes. Forspecific examples of formatting standards the reader is referred to RickPoyner, LGC/Telegraphics, “Wintab™ Interface Specification: 16-bit and32-bit API Reference”, revision of May 9, 1996; Universal Serial Bus(USB), “Device Class Definition for Human Interface Devices (HID)”,Firmware Specification, USB Implementers' Forum, Jun. 27, 2001 andsix-degree of freedom interface by Ulrica Larsson and JohannaPettersson, “Development and evaluation of a 6DOF interface to be usedin a medical application”, Thesis, Linkopings University, Department ofScience and Technology, Sweden, Jun. 5, 2002.

The orientation portion of absolute pose data 12, i.e., Euler angles (φ,θ, ψ) can also be used in the present embodiment. Specifically,processor 26 can prepare additional subsets or send all of theorientation parameters (φ, θ, ψ) of absolute pose data 12 as a singlesubset to application 28 or to a different application or device servinga different function. Any mix of orientation (φ, θ, ψ) and position (x,y, z) data derived from absolute pose data 12 can be used in subset 48.In fact, in some embodiments processor 26 keeps all absolute pose data12 in subset 48 such that all of its parameters (φ, θ, ψ, x, y, z) canbe used by application 28. This is done when application 28 has toreconstruct the entire motion 40 of pointer 14 and not just trace 42 oftip 16. For example, this is done when application 28 includes amotion-capture application. Once again, the temporal resolution ofmotion 40 can be improved by increasing the frequency of measurementtimes t_(i). Note that in this case parameters of pose data 12 that varyslowly are oversampled.

In FIG. 3 a block diagram illustrates the processing of absolute posedata 12 by processor 26 and its use by application 28 in more detail. Ina first step 50, absolute pose data 12 is received by processor 26 viacommunication link 24. In a second step 52, processor 26 determineswhich portion or subset 48 of absolute pose data 12 is required. Thisselection can be made based on application 28. For example, whenapplication 28 is a trace-capture application that charts trace 42, thenonly position data of tip 16, i.e., (x, y, z) of this reference point 16need to be contained in subset 48. On the other hand, when application28 is a motion-capture application, then all absolute pose data 12 arecontained in subset 48.

In step 58 all absolute pose data 12 are selected and passed to a subsetformatting or preparing step 60A. In step 60A data 12 is prepared in theform of subset 48A as required by application 28. For example, data 12is arranged in a particular order and provided with appropriate footer,header and redundancy bits (not shown), or as otherwise indicated bydata porting standards such as those of Rick Poyner, LGC/Telegraphics(op. cit.).

In step 62, only a portion of data 12 is selected. Three exemplary casesof partial selection are shown. In the first case, only position data isrequired by application 28. Hence, in a step 59B only position data (x,y, z) are selected and the remaining data 12 is discarded. In asubsequent step 60B, position data (x, y, z) are prepared in the form ofsubset 48B as required by application 28 and/or as dictated by theporting standards.

In a second case, in a step 59C, only orientation data (φ, θ, ψ) areselected and the rest of data 12 are discarded. Then, in a step 60C,orientation data (φ, θ, ψ) are prepared in the form of a subset 48C foruse by application 28.

In the third case, in a step 59D, a mix of data 12, including someposition data and some orientation data are selected and processedcorrespondingly in a step 60D to prepare a subset 48D.

A person skilled in the art will appreciate that the functions describedcan be shared between processor 26 and application 28, e.g., as requiredby the system architecture and data porting standards. For example, somepreparation of subset 48 can be performed by application 28 uponreceipt. It should also be noted that in some embodiments data 12 can bepre-processed by transmitter 30 or post-processed at any point before orafter preparation of the corresponding subset 48 in accordance with anysuitable algorithm. For example, a statistical algorithm, such as aleast squares fit can be applied to data 12 derived at different timest_(i) or to successive subsets 48. Furthermore, quantities such as timederivatives of any or all parameters, i.e.,

$\left( {\frac{\mathbb{d}x}{\mathbb{d}t},\frac{\mathbb{d}y}{\mathbb{d}t},\frac{\mathbb{d}z}{\mathbb{d}t},\frac{\mathbb{d}\phi}{\mathbb{d}t},\frac{\mathbb{d}\theta}{\mathbb{d}t},\frac{\mathbb{d}\psi}{\mathbb{d}t}} \right),$can be computed. Also, various sampling techniques, e.g., oversamplingcan be used.

Subset 48 is transmitted to application 28 via a communication channel72. Application 28 receives subset 48 as an input that is treated orrouted according to its use. For example, in a step 64, subset 48 isused as control data. Thus, subset 48 is interpreted as an executablecommand 66 or as a part of an executable command. On the other hand, ina step 68, subset 48 is used as input data and saved to a data file 70.

In one embodiment, application 28 passes information to processor 26 tochange the selection criteria for subset 48. Such information can bepassed via communication channel 72 or over an alternative link, e.g., afeedback link 74. For example, application 28 requests subset 48A to betransmitted and uses subset 48A as input data for data file 70. At othertimes, application 28 requests subset 48C to be transmitted and usessubset 48C as command data for executable command 66. Alternatively,processor 26 can indicate a priori whether any subset 48 should betreated as input data or control data. In still another alternative,user 38 can indicate with the aid of a separate apparatus, e.g., aswitch mounted on pointer 14 (not shown), whether subset 48 is intendedas control data or input data. A person skilled in the art willrecognize that there exist a large number of active and passive methodsfor determining the interpretation and handling of data beingtransmitted in subset 48 by both processor 26 and application 28.

In a specific application 28, subset 48 contains only position data (x,y, z) of reference point or tip 16 of pointer 14 collected at a numberof measurement times t_(i). This subset corresponds to individual pointsalong trace 42 and is an absolute trace expressed by points referencedwith respect to origin (0, 0, 0) of world coordinates (X_(o), Y_(o),Z_(o)). For example, in a particular applications 28 trace 42 may betreated as a digital ink trace that is designed to be handled as inputdata or command data. Alternatively, the absolute points forming trace42 can be expressed in world coordinates (X_(o), Y_(o), Z_(o)) withrespect to a reference location other than world origin (0, 0, 0). FIG.1 shows that one such alternative reference location can be the centerof feature 34, whose absolute position in world coordinates (X_(o),Y_(o), Z_(o)) is known. In this case, vectors D_(o), . . . D_(i), . . .D_(n) describe the absolute position of the points of trace 42 collectedat successive measurement times t_(o), . . . t_(i), . . . t_(n).

In practice, efficient inference of the absolute pose of pointer 14 interms of absolute pose data expressed in parameters (φ, θ, ψ, x, y, z)representing Euler rotated object coordinates expressed in worldcoordinates (X_(o), Y_(o), Z_(o)) with respect to a reference location,such as world origin (0, 0, 0) imposes a number of importantrequirements. Since pointer 14 may be moving in a close-rangeenvironment 18 the field of view of on-board optical measuringarrangement 22 must be large. This is particularly crucial in situationswhere arrangement 22 has to tolerate frequent occlusions of one or moreof invariant features 32, 34, 36. Such conditions arise when user 38operates pointer 14 in a close-range home, gaming or work environment18, i.e., in a room, a cubicle or other confined real space. Also, iffull motion capture is desired, then the rate or frequency ofmeasurement times t_(i) has to be high in comparison to the rate ofmovement of the hand of user 38.

To learn how to address these and other practical considerations, weturn to another embodiment of an apparatus 100 according to theinvention as shown in FIG. 4. Apparatus 100 has a manipulated object 102equipped with an on-board optical measuring arrangement 104 having alight-measuring component 106. Apparatus 100 is deployed within a realthree-dimensional environment 108. In the case at hand, environment 108is defined within a room 110 and it is parametrized by global or worldcoordinates (X_(o), Y_(o), Z_(o)) whose world origin (0, 0, 0) isposited in the lower left rear corner of room 110.

As in the previous embodiment, world origin (0, 0, 0) is selected as thereference location for expressing the measured values of parameters (φ,θ, ψ, x, y, z) that represent absolute pose data of manipulated object102 in Euler rotated object coordinates (X, Y, Z). The three successiverotations by Euler angles (φ, θ, ψ) to obtain Euler rotated objectcoordinates (X, Y, Z) are also indicated in FIG. 4. Also, the original(X′, Y′, Z′), the once rotated (X″, Y″, Z″), and the twice rotated (X′″,Y′″, Z′″) object coordinates are drawn along the fully Euler rotated(three times rotated) object coordinates (X, Y, Z). Just like in theprevious embodiment, a tip 102′ of manipulated object 102 is chosen asthe reference point. Conveniently, a vector G_(o) describes the positionof reference point 102′ in world coordinates (X_(o), Y_(o), Z_(o)).

A number of invariant features B1-B7 are placed at known locations inreal three-dimensional environment 108 delimited by room 110. VectorsR1-R7 define the locations of corresponding invariant features B1-B7.Following standard convention, vectors R1-R7 extend from world origin(0, 0, 0) to the centers of the corresponding invariant features B1-B7.All seven invariant features B1-B7 are high optical contrast features.More precisely, invariant features B1-B7 are light sources such aslight-emitting diodes that emit electromagnetic radiation or light 112.Preferably, light 112 is in the infrared wavelength range of theelectromagnetic spectrum. Light-emitting diodes in that range aretypically referred to as infrared emitting diodes or just IR LEDs. Forclarity, only four of the seven IR LEDs B1-B7 are shown simultaneouslyemitting light 112 in FIG. 4.

Optical measuring arrangement 104 with light-measuring component 106 ismounted on-board, and more precisely on one of the sides of manipulatedobject 102. Component 106 is an absolute motion detection componentequipped with a lens 114 and an optical sensor 116 shown in detail inthe cut-away view of manipulated object 102 depicted in FIG. 5. Lens 114faces environment 108 and it has a wide field of view. For example, lens114 is a fisheye lens whose field of view (F.O.V.) is large enough toview all or nearly all IR LEDs B1-B7 in environment 108 from allabsolute poses that it is anticipated to assume while being manipulatedby a user (not shown in this drawing).

It should be noted, however, that the handling of manipulated object 102does not need to be carried out directly by a user. In fact, object 102can be a remotely controlled object or even an object that is cast orthrown by the user. Whether object 102 is manipulated directly orremotely and whatever its spatial trajectory in environment 108, it iscrucial that light-measuring component 106 be optimally placed on object102 to have a direct line-of-sight to most or all IR LEDs B1-B7 whileobject 102 is undergoing its intended motion. That is because component106 needs to capture light 112 emitted by IR LEDs B1-B7 so that it canuse these invariant features for optically inferring the values ofparameters (φ, θ, ψ, x, y, z). Taken together, parameters (φ, θ, ψ, x,y, z) represent absolute pose data 118 that describes the absolute poseof manipulated object 102.

An appropriate choice of lens 114 will aid in addressing the aboveoptics challenges. Obviously, lens 114 has to be small, robust andlow-cost (e.g., moldable in acrylic or other plastic). Lens 114 shouldnot require active focusing and it should have a low F-number (e.g.,F#≈1.6 or less) to ensure high light gathering efficiency. At the sametime, lens 114 should exhibit low levels of aberration and have a singleviewpoint. In other words, lens 114 should exhibit quasi-pinhole opticalcharacteristics. This last attribute is especially important whenmanipulated object 102 is expected to sometimes pass within a shortdistance of IR LEDs B1-B7. Under such conditions, the limited depth offield inherent in a normal refractive lens, especially one withoutactive focal length adjustment, would cause a loss of opticalinformation; a familiar problem in machine vision. U.S. Pat. Nos.7,038,846 and 7,268,956, both to Mandella, teach a suitable design of acatadioptric lens that satisfies these stringent demands. Apparatus 100has a processor 120 for preparing pose data 118.

In this exemplary embodiment, processor 120 is not on-board manipulatedobject 102 but is instead integrated in a computing device 122. Forexample, processor 120 may be a central processing unit (CPU), agraphics processing unit (GPU) or some other unit or combination ofunits resident on computing device 122. Computing device 122 is shown asa stationary device, but it is understood that it could be a portabledevice or an ultra-mobile device including a tablet, a PDA or a cellphone.

Besides preparing absolute pose data 118, processor 120 is entrustedwith identifying a subset 118′ of data 118. As in the prior embodiment,the preparation of data 118 may include just collecting the inferredvalues of parameters (φ, θ, ψ, x, y, z) corresponding to the absolutepose of object 102. In more involved cases, the preparation of data 118can include pre- and/or post-processing as well as computation offunctions derived from measured values of one or more of parameters (φ,θ, ψ, x, y, z) (including the application of statistical algorithms toone or more these parameters). Meanwhile, identification of subset 118has to do with the intended use of data 118 and the nature of itsapplication.

Computing device 122 not only hosts processor 120, but also has adisplay 124 for displaying an output 126 to the user. Output 126 isgenerated by an application 128 that is running on computing device 122.Application 128 and its output 126 dictate what subset 118′ needs to beidentified and supplied by processor 120. A simple case arises whenapplication 128 is configured to produce as output 126 a visual elementsuch as a token or even an image of object 102 and compute as well asshow its absolute trajectory within room 110 in world coordinates(X_(o), Y_(o), Z_(o)) with respect to reference location (0, 0, 0). Aperson skilled in the art will easily discern, that under theseconstraints application 128 will require that all parameters (φ, θ, ψ,x, y, z) be included in subset 118′. This way, as time progresses,application 128 will be able to alter output 126 in response to theabsolute pose of object 102 at different times t_(i) and, if desired,display a replica of its full trajectory within room 110. Application128 can display this information as output 126 on display 124 to theuser as shown in FIG. 4 or forward the information to still anotherapplication.

Computing device 122 employs its own internal communication link 130,e.g., a data bus, to transmit subset 118′ to application 128. Meanwhile,a wireless communication link 132 is provided for transmitting data 118from manipulated object 102 to computing device 122. Wireless link 132employs a transmitting unit 134A on object 102 and a receiving unit 134Bon device 122.

When manipulated object 102 moves within room 110 on-board opticalmeasuring arrangement 104 deploys absolute motion detection component106. Here, component 106 is a light-measuring component that gatherslight 112 emitted from IR LEDs B1-B7. Preferably, all IR LEDs B1-B7 areon at measurement times t_(i) when the values of parameters (φ, θ, ψ, x,y, z) describing the absolute pose of object 102 are being measured.

As shown in more detail in FIG. 5, light-measuring component 106collects light 112 within the field of view of lens 114. Preferably,lens 114 has a single viewpoint 136 and is configured to image room 110onto optical sensor 116. Thus, lens 114 images light 112 from IR LEDsB1-B7 onto its optical sensor. For reasons of clarity, light 112 fromjust one IR LED is shown as it is being collected and imaged to an imagepoint 140 on optical sensor 116 by lens 114. Sensor 116 can be any typeof suitable light-sensitive sensor, such as a CCD or CMOS sensor coupledwith appropriate image processing electronics 142.

Electronics 142 can either fully process signals from sensor 116, oronly pre-process them to obtain raw image data. The choice depends onwhether fully processed or raw absolute pose data 118 is to betransmitted via wireless link 132 to computing device 122. Whensufficient on-board power is available, performing most or all imageprocessing functions on-board object 102 is desirable. In this caseelectronics 142 include all suitable image processing modules to obtainmeasured values of parameters (φ, θ, ψ, x, y, z) in their final numericform. Data 118 being transmitted via link 132 to computing device 122under these conditions is very compact. On the other hand, when on-boardpower is limited while the bandwidth of wireless communication link 132is adequate, then electronics 142 include only the image processingmodules that extract raw image data from sensor 116. In this case, rawabsolute pose data 118 is transmitted to computing device 122 forfurther image processing to obtain the inferred or measured values ofparameters (φ, θ, ψ, x, y, z) in their final numeric form.

In the present embodiment, sensor 116 is a CMOS sensor with a number oflight-sensing pixels 144 arranged in an array 145, as shown in FIG. 6.The field of view of lens 112 is designated by F.O.V. and it isindicated on the surface of sensor 116 with a dashed line. Imageprocessing electronics 142 are basic and designed to just capture rawimage data 146 from pixels 144 of sensor 116. In particular, electronics142 have a row multiplexing block 148A, a column multiplexing block 148Band a demultiplexer 150.

The additional image processing modules depicted in FIG. 6 and requiredto obtain data 118 in its final numeric form and to identify subset 118′for application 128 all reside on computing device 122. These modulesinclude: extraction of IR LEDs (module 152) from raw image data 146,image undistortion and application of the rules of perspective geometry(module 154), computation of pose data 118 or extraction of inferred ormeasured values of parameters (φ, θ, ψ, x, y, z) (module 156) andidentification of subset 118′ (module 158). Note that different imageprocessing modules may be required if invariant features aregeometrically more complex than IR LEDs B1-B7, which are mere pointsources.

For example, extraction of invariant features such as edges, corners andmarkings will require the application of suitable image segmentationmodules, contrast thresholds, line detection algorithms (e.g., Houghtransformations) and many others. For more information on edge detectionin images and edge detection algorithms the reader is referred to U.S.Pat. Nos. 6,023,291 and 6,408,109 and to Simon Baker and Shree K. Nayar,“Global Measures of Coherence for Edge Detector Evaluation”, Conferenceon Computer Vision and Pattern Recognition, June 1999, Vol. 2, pp.373-379 and J. Canny, “A Computational Approach to Edge Detection”, IEEETransactions on Pattern Analysis and Machine Intelligence, Vol. 8, No.6, November 1986 for basic edge detection all of which are hereinincorporated by reference. Additional useful teachings can be found inU.S. Pat. No. 7,203,384 to Carl and U.S. Pat. No. 7,023,536 to Zhang etal. A person skilled in the art will find all the required modules instandard image processing libraries such as OpenCV (Open Source ComputerVision), a library of programming functions for real time computervision. For more information on OpenCV the reader is referred to G. R.Bradski and A. Kaehler, “Learning OpenCV: Computer Vision with theOpenCV Library”, O'Reilly, 2008.

In the present embodiment, the absolute pose of object 102 including thephysical location (x, y, z) of reference point 102′ (described by vectorG_(o)) and the Euler angles (φ, θ, ψ) are inferred with respect to worldorigin (0, 0, 0) with the aid of vectors R1-R7. To actually computethese parameters from on-board object 102 it is necessary to recovervectors R1-R7 from images 140 of IR LEDs B1-B7 contained in an image 160of room 110 as shown on the surface of sensor 116 in FIG. 6. Thisprocess is simplified by describing image 160 in image coordinates(X_(i), Y_(i)). Note that due to an occlusion 162, only images 140 of IRLEDs B1-B4, B6, B7 associated with image vectors R1′-R4′, R6′, R7′ areproperly imaged by lens 114 onto sensor 116.

In practical situations, occlusion 162 as well as any other occlusionscan be due to the user's body or other real entities or beings presentin environment 108 obstructing the line-of-sight between lens 114 and IRLED B5. Also note, that if too few of IR LEDs B1-B7 are imaged, theninference of the absolute pose of object 102 may be impossible due toinsufficient data. This problem becomes particularly acute if IR LEDsB1-B7 are not distinguishable from each other. Therefore, in a practicalapplication it is important to always provide a sufficiently largenumber of IR LEDs that are suitably distributed within environment 108.Alternatively or in addition to these precautions, IR LEDs B1-B7 can bemade distinguishable by setting them to emit light 112 at differentwavelengths.

Referring again to FIG. 6, in a first image processing step electronics142 demultiplex raw image data 146 from row and column blocks 148A, 148Bof array 145 with the aid of demultiplexer 150. Next, wirelesscommunication link 132 transmits raw image data 146 from on-board object102 to computing device 122. There, raw image data 146 is processed bymodule 152 to extract images 140 of IR LEDs B1-B7 from raw image data146. Then, module 154 undistorts the image and applies the rules ofperspective geometry to determine the mapping of images 140 of IR LEDsB1-B7 to their actual locations in real three-dimensional environment108 of room 110. In other words, module 154 recovers vectors R1-R7 fromimage vectors R1′-R7′.

To properly perform its function, module 154 needs to calibrate thelocation of the center of image coordinates (X_(i), Y_(i)) with respectto reference point 102′. This calibration is preferably done prior tomanipulating object 102, e.g., during first initialization and testingor whenever re-calibration of origin location becomes necessary due tomechanical reasons. The initialization can be performed with the aid ofany suitable algorithm for fixing the center of an imaging system. Forfurther information the reader is referred to Carlo Tomasi and JohnZhang, “How to Rotate a Camera”, Computer Science DepartmentPublication, Stanford University and Berthold K. P. Horn, “Tsai's CameraCalibration Method Revisited”, which are herein incorporated byreference.

Armed with the mapping provided by module 154, module 156 obtains theinferred values of parameters (φ, θ, ψ, x, y, z), which representabsolute pose data 118. Data 118 now properly represents the finalnumerical result that describes the inferred absolute pose of object102. This description is made in terms of inferred values of parameters(φ, θ, ψ, x, y, z), which are the Euler rotated object coordinatesexpressed in world coordinates (X_(o), Y_(o), Z_(o)) with respect toworld origin (0, 0, 0). In the last step, module 158 identifies a subset118′ of parameters (φ, θ, ψ, x, y, z) to be sent to application 128.

In practice, due to certain optical effects including aberrationassociated with lens 114, the non-occluded portion of image 160 willexhibit a certain amount of rounding. This rounding can be compensatedoptically by additional lenses (not shown) and/or electronically duringundistortion performed by module 154. Preferably, the rounding isaccounted for by applying a transformation to the non-occluded anddetected portion of image 160 by module 154. For example, module 154 hasan image deformation transformer based on a plane projection to producea perspective view. Alternatively, module 154 has an image deformationtransformer based on a spherical projection to produce a sphericalprojection. Advantageously, such spherical projection can be transformedto a plane projection with the aid of well-known methods, e.g., asdescribed by Christopher Geyer and Kostas Daniilidis, “A Unifying Theoryfor Central Panoramic Systems and Practical Implications”,www.cis.upenn.edu, Omid Shakernia, et al., “Infinitesimal MotionEstimation from Multiple Central Panoramic Views”, Department of EECS,University of California, Berkeley, and Adnan Ansar and KostasDaniilidis, “Linear Pose Estimation from Points or Lines”, JetPropulsion Laboratory, California Institute of Technology and GRASPLaboratory, University of Pennsylvania which are herein incorporated byreference.

It should also be remarked, that once image 160 is recognized andtransformed, a part of the orientation, namely Euler angles (φ, θ) ofobject 102 can be inferred in several ways. For example, when workingwith the spherical projection, i.e., with the spherical projection ofunobstructed portions of image 160, a direct three-dimensional rotationestimation can be applied to recover inclination angle θ and polar angleφ. For this purpose a normal view of room 110 with IR LEDs B1-B7 isstored in a memory (not shown) such that it is available to module 154for reference purposes. The transformation then yields the Euler angles(φ, θ) of object 102 with respect to IR LEDs B1-B7 and any other highoptical contrast invariant features in room 110 by applying thegeneralized shift theorem. This theorem is related to the Euler theoremstating that any motion in three-dimensional space with one point fixed(in this case the reference point 102′ may be considered fixed for theduration of one measurement time t_(i)) can be described by a rotationabout some axis. For more information about the shift theorem the readeris referred to Ameesh Makadia and Kostas Daniilidis, “Direct 3D-RotationEstimation from Spherical Images via a Generalized Shift Theorem”,Department of Computer and Information Science, University ofPennsylvania, which is herein incorporated by reference.

Alternatively, when working with a plane projection producing aperspective view of unobstructed portions of image 160 one can usestandard rules of geometry to determine inclination angle θ and polarangle φ. Several well-known geometrical methods taking advantage of therules of perspective views can be employed in this case.

Referring back to FIGS. 4 and 5, in the present embodiment, output 126includes a visual element, namely an image of object 102. Since subset118′ contains all parameters (φ, θ, ψ, x, y, z) and is gathered at manysuccessive measurement times t_(i), visual element representing object102 can be shown undergoing its absolute motion in world coordinates(X_(o), Y_(o), Z_(o)) For example, in the present case a trajectory 162Aof reference point or tip 102′ is shown on display 124. In addition, atrajectory 162B of the center of mass designated by C.O.M. could also bedisplayed on display 124. Depending on application 128, the absolutemotion of object 102 could be replayed in parts or in its entirety atnormal speed or at an altered rate (slowed down or sped up).

A person skilled in the art will realize that the embodiment ofapparatus 100 shown in FIGS. 4-6 is very general. It admits of manyvariants, both in terms of hardware and software. Practicalimplementations of the apparatus and method of invention will have to bedictated by the usual limiting factors such as weight, size, powerconsumption, computational load, overall complexity, cost, desiredabsolute pose accuracy and so on. Among other, these factors willdictate which type of senor and lens to deploy, and whether most of theimage processing should take place on-board object 102 or in computingdevice 122.

Another embodiment of an apparatus 200 in accordance with the inventionis shown in the three-dimensional diagrammatical view of FIG. 7.Apparatus 200 represents a preferred embodiment of the invention andaddresses several of the above-mentioned limiting factors. Inparticular, apparatus 200 introduces practical simplifications that canbe used under numerous circumstances to obtain absolute pose of amanipulated object 202 (only partially shown here for reasons ofclarity) that moves in a real three-dimensional environment 204.Environment 204 is described by global or world coordinates (X_(o),Y_(o), Z_(o)). Their origin (0, 0, 0) is chosen as the referencelocation for apparatus 200 with respect to which the absolute pose orseries of absolute poses at different measurement times t_(i) areexpressed.

Environment 204 is an outdoor environment with ambient light 220provided by the sun over the usual solar spectral range Δλ_(amb). Acertain number n of invariant features B1-Bn are affixed at knownlocations in environment 204. Vectors b1-bn are employed to describe thelocations of corresponding invariant features B1-Bn in world coordinates(X_(o), Y_(o), Z_(o)). All invariant features B1-Bn are high opticalcontrast features, and, more specifically, they are IR LEDs for emittingelectromagnetic radiation or light 222 in the infrared range of theelectromagnetic spectrum.

When invariant features are embodied by light sources that arecontrolled they will be referred to as beacons. Beacons are preferablyone-dimensional or point-like and they are implemented by light emittingdiodes (LEDs), laser diodes, IR LEDs, optical fibers and the like. Ofcourse, beacons can also be extended sources such as lamps, screens,displays and other light sources as well as any objects providingsufficiently highly levels of electromagnetic radiation that can becontrolled. These include projected points and objects, as well aspoints and objects concentrating and reflecting radiation originating inenvironment 204 or active illumination from on-board manipulated object202. The advantage of beacons over simple and uncontrolled light sourcesis that they are distinguishable.

It is the emission pattern of beacons B1-Bn that is controlled in thepresent embodiment. Hence, they are distinguishable and play the role ofbeacons. The emission pattern of beacons B1-Bn is dictated by locationsb1-bn at which they are affixed in environment 204 and their on/offtiming. In other words, the emission pattern is spatially set by placingbeacons B1-Bn at certain locations and it is temporally varied byturning the beacons on and off at certain times.

Beacons B1, B2, . . . , Bn are controlled by corresponding controls C1,C2, . . . , Cn and a central unit 224 that communicates with thecontrols. The communications between unit 224 and controls C1, C2, . . ., Cn are carried by wireless up-link and down-link signals 226A, 226B.Of course, any method of communication, including wired or optical, canbe implemented between central unit 224 and controls C1, C2, . . . , Cn.Different communication equipment will typically require differentsupporting circuitry, as will be appreciated by those skilled in theart. Taken together, controls C1, C2, . . . , Cn and unit 224 form anadjustment mechanism 228 for setting or adjusting a sequenced emissionpattern of IR LEDs B1, B2, . . . , Bn. In other words, adjustmentmechanism 228 is capable of modulating all IR LEDs B1-Bn in accordancewith a pattern.

Object 202 has an on-board optical measuring arrangement 206 consistingof an absolute motion detection component 208. Component 208 is alight-measuring component with a lens 210 and an optical sensor 212.Light-measuring component 208 has an optical filter 216 positionedbefore sensor 212, as well as image processing electronics 218 connectedto sensor 212. As in the prior embodiment, lens 210 is preferably a widefield of view lens with a substantially single viewpoint 214. Viewpoint214 is selected as the reference point on manipulated object 202 forexpressing the location parameters (x, y, z) of its absolute pose andits orientation parameters (φ, θ, ψ). Hence, vector G_(o) in thisembodiment extends from world origin (0, 0, 0) to viewpoint 214.

Once again, the absolute pose of object 202 in this embodiment isexpressed in the Euler rotated object coordinates (X, Y, Z), whoseorigin is now attached to viewpoint 214. The manner in which rotationsby Euler angles (φ, θ, ψ) are applied to object 202 to express the Eulerrotated object coordinates (X, Y, Z) are analogous to the conventionexplained above and will therefore not be repeated.

The choice of viewpoint 214 of lens 210 as the reference point is veryconvenient for tracking object 202 and it does not limit the choice ofobject coordinates, as will be appreciated by those skilled in the art.As before, the absolute pose of object 202 is completely described bysix parameters, namely the three components (x, y, z) of displacementvector G_(o) from the origin of global coordinates (X_(o), Y_(o), Z_(o))to the reference point, in this case viewpoint 214, and the three Eulerangles (φ, θ, ψ). A trajectory 230 of object 202 is thus fully describedby these six parameters and time t, i.e., (x, y, z, φ, θ, ψ, t).

Notice that lens 210, although shown as a single element in the previousand current embodiments can be compound. In other words, lens 210 canconsist of several optical elements including various combinations ofrefractive and reflective elements. In any of these embodiments, theeffective viewpoint 214 can be determined and chosen as reference pointon object 202.

Optical sensor 212 of absolute motion detection component 208 is aphotosensor designed for sensing light 222 from IR LEDs B1-Bn. In fact,rather than being a sensor with an array of pixels, photosensor 212 is acentroid sensing device or the so-called position-sensing device (PSD)that determines a centroid of the flux of light 222 impinging on it.

Lens 210 has a field of view sufficiently large to captureelectromagnetic radiation or light 222 emitted by most or all beaconsB1-Bn and image it onto on-board centroid sensing device or PSD 212.Mathematically, it is known that to infer the absolute pose of object202, i.e., to infer or measure the values of all parameters (x, y, z, φ,θ, ψ) of object 202 in environment 204, at least four amongdistinguishable beacons B1-Bn need to be in the field of view of lens210.

Optical filter 216 placed before PSD 212 reduces the level of ambientlight 220 impinging on PSD 212. Concurrently, the wavelengths ofelectromagnetic radiation or light 222 provided by LEDs B1-Bn areselected such that they are passed by filter 216. In the present case,ambient radiation 220 is produced by the sun and spans an emissionspectrum Δλ_(amb.), whose intensity (I) peaks in the visible range anddrops off in the infrared range as generally shown by graph 250 in FIG.8A. Consequently, it is advantageous to select the wavelengths λ₁, λ₂, .. . , λ_(n) of electromagnetic radiation 222 emitted by LEDs B1-Bn toreside in an infrared range 252.

It is optional whether all wavelengths λ₁, λ₂, . . . , λ_(n) aredifferent or equal. In some embodiments, different wavelengths can beused to further help differentiate between IR LEDs B1-Bn. In the presentembodiment, however, all IR LEDs B1-Bn are emitting at the same emissionwavelength λ_(e) equal to 950 nm. A transmittance (T) of filter 216 isselected as shown by graph 254 in FIG. 8B, so that all wavelengths ininfrared range 252, including λ_(e) in particular pass through.Wavelengths in the far infrared range upwards of 1,000 nm where ambientradiation 220 is even weaker can also be used if a higher signal tobackground ratio is desired.

Returning to FIG. 7, we see how electromagnetic radiation 222 at thewavelength of 950 nm emitted by beacon B4 passes filter 216 and isimaged onto PSD 212. PSD 212 can be selected from a large group ofcandidates including, for example, devices such as semiconductor-typeposition sensitive detectors (PSDs), optical waveguide-based positionsensitive detectors and organic material position sensitive detectors.In the present embodiment, device 212 is a semiconductor-type positionsensitive detector (PSD) employing a reverse biased p-n junction.

Lens 210 produces an imaged distribution 232 of electromagneticradiation 222 on PSD 212. PDS 212, in turn, generates electrical signalsthat represent the x-y position of a center-of-mass or centroid 234 ofimaged distribution 232 in x-y plane of PSD 212. In the present case, IRLED B4 is a point-like source of electromagnetic radiation 222 andtherefore lens 210 images it to a spot-type distribution 232. Ingeneral, it is desirable to keep spot 232 relatively small byappropriate design of lens 210, which is preferably a lens with goodimaging properties including low aberration, single viewpoint imagingand high-performance modulation transfer function (MTF). In general,however, optic 210 can be refractive, reflective or catadioptric.

For a better understanding of PSD 212 we turn to the plan view diagramof its top surface 236 shown in FIG. 9. To distinguish coordinates inthe image plane that is coplanar with top surface 236 of PSD 212, theimage coordinates are designated (X_(i), Y_(i)). Note that the field ofview (F.O.V.) of lens 210 is designated in a dashed line and isinscribed within the rectangular surface 236 of PSD 212. This means thatthe entire F.O.V. of lens 210 is imaged onto PSD 212. In an alternativeembodiment, the F.O.V. may circumscribe surface 236, as indicated in thedashed and dotted line. Under this condition, the image of some beaconsmay not fall on the surface of PSD 212. Thus, the information from thesebeacons will not be useful in optically inferring the absolute pose ofobject 202.

PSD 212 has two electrodes 238A, 238B for deriving signals correspondingto the x-position, namely x_(i) ⁺ and x_(i) ⁻, and two electrodes 238C,238D for obtaining y_(i) ⁺ and y_(i) ⁻ signals corresponding to they-position. The manner in which these signals are generated andprocessed to obtain the location (x_(i), y_(i)) of centroid 234 iswell-known to those skilled in the art and will not be discussed herein.For more information on the subject the reader is referred tomanufacturer-specific PSD literature, such as, e.g., “PSD (PositionSensitive Detector)” Selection Guide of Hamamatsu, Solid State Division,July 2003.

The intensities 232X, 232Y of imaged distribution 232, i.e., spot 232,along the X_(i) and Y_(i) axes are visualized along the sides. Anotherimaged distribution 240 due to ambient radiation 220 is also indicatedwith a dashed line. Corresponding intensities 240X, 240Y along the X_(i)and Y_(i) axes are also visualized along the sides. Because of theaction of filter 216, intensities 240X, 240Y are low in comparison to232X, 232Y and the corresponding centroid position thus includes anegligibly small shift error due to the background noise on the desiredsignal. Such background can be removed with any well-known electronicfiltering technique, e.g., standard background subtraction.Corresponding electronics are known and will not be discussed herein.

PSD 212 is connected to image processing electronics 218 and deliverssignals x_(i) ⁺, x_(i) ⁻, and y_(i) ⁺, y_(i) ⁻ to it. Electronics 218are also in communication with central unit 224 by any suitable link sothat it knows which beacon is active (here beacon B4) and thusresponsible for centroid 234 at any given time. It is convenient toestablish the link wirelessly with up-link and down-link signals 226A,226B, as shown in FIG. 7.

During operation, optical apparatus 200 uses the knowledge of whichbeacon produces centroid 234 described by image coordinates (x_(i),y_(i)) and the beacon's location in environment 204 or world coordinates(X_(o), Y_(o), Z_(o)) to infer the absolute pose of object 202 in termsof measured values of parameters (x, y, z, φ, θ, ψ). Note that beaconsB1-Bn need not be attached or affixed at any permanent location inenvironment 204, as long as their location at the time of emission ofradiation 222 is known to apparatus 200. Moreover, any sequenced patternof beacons B1-Bn can be used, even a pattern calling for all beaconsB1-Bn to be on simultaneously. In the latter case, a constellation of nspots is imaged on PSD 212 and centroid 234 is the center of mass(C.O.M.) of the entire constellation of n spots 232, i.e., it is notassociated with a single spot. Of course, in that case the ability todistinguish the beacons is removed and the performance of apparatus 200will be negatively affected.

For better clarity of explanation, we first consider a modulation orsequenced pattern with only one beacon on at a time. Following suchpattern, beacon B4 is turned off and beacon Bm is turned on to emitradiation 222. Note that an intensity distribution 242 of radiation 222has a wide cone angle such that lens 210 can image radiation 222 even atsteep angles of incidence. Alternatively, given knowledge of allpossible relative positions between object 202 and beacon Bm, amechanism can be provided to optimize angular distribution 242 forcapture by lens 210.

To commence motion capture, controls C1-Cn and unit 224, i.e.,adjustment mechanism 228 implements an initial sequenced pattern of IRLEDs B1-Bn. The initial pattern can be provided by image processingelectronics 218 to unit 224 of adjustment mechanism 228 via up-linksignals 226A. The initial pattern can be based on any parameter of thelast known or inferred absolute pose or any other tracking information.Alternatively, initial sequenced pattern is standard.

A flow diagram in FIG. 10 illustrates the steps of an exemplary absolutepose and motion capture program 270 implemented by image processingelectronics 218 and mechanism 228. Algorithm 270 commences withactivation of initial modulation according to sequenced pattern 272 forone cycle and synchronization of electronics 218 with mechanism 228 instep 274. This is done by matching signals x_(i) ⁺, x_(i) ⁻, and y_(i)⁺, y_(i) ⁻ delivered by PSD 212 to electronics 218 with each activebeacon as individual beacons B1, B2, . . . , Bn are turned on and off bycontrols C1, C2, . . . , Cn in accordance with initial sequencedpattern. Drop out of any one beacon is tolerated, as long assynchronization with at least four beacons is confirmed for absolutepose capture or fewer than four but at least one for relative posedetermination.

Motion capture starts in step 276. In step 278 signals x_(i) ⁺, x_(i) ⁻,and y_(i) ⁺, y_(i) ⁻ encoding centroid 234 of activated beacon are sentfrom PSD 212 to electronics 218 for processing. In step 280 signals aretested for presence (sufficient power level for further processing) andare then filtered in step 282 to obtain filtered data corresponding tocentroid 234. Filtering includes background subtraction, signal gaincontrol including lock-in amplification and/or other typical signalprocessing functions. Absence of signals x_(i+), x_(i) ⁻, and y_(i) ⁺,y_(i) ⁻ is used to flag the corresponding beacon in step 284.

After filtering, the data is normalized in step 286. This step involvestime-stamping, removing effects of known optical aberrations due to lens210 and preparing the data for processing by either absolute or relativetracking or navigation algorithms. Normalization also formats datapoints from each cycle and may include buffering the data, if necessary,while centroid 234 from the next beacon in the pattern is queued up orbuffering until a sufficient number of centroids 234 have been capturedto perform reliable normalization. In a preferred embodiment, beaconsB1, B2, . . . , Bn are amplitude modulated with a series of pulses. Inthis embodiment, normalization further includes selection of the pulsewith most suitable amplitude characteristics (e.g., full dynamic rangebut no saturation) and discarding signals from other pulses.

In step 288 normalized data of centroid 234 is sent to a tracking ornavigation algorithm 290. Contemporaneously, or earlier depending ontiming and buffering requirements, absolute pose and motion captureprogram 270 submits a query 292 whether the first cycle of initialsequenced pattern in complete. The answer is used by navigationalgorithm 290 in determining at least one parameter of the pose ofobject 202 and to prepare for capturing the next centroid in step 294.

Navigation algorithm 290 preferably determines all parameters (x, y, z,φ, θ, ψ) at initialization time t_(init). in global coordinates (X_(o),Y_(o), Z_(o)) based on known locations of beacons B1, B2, . . . , Bn,i.e., known vectors b1, b2, . . . , bn. Only centroids 234 that areavailable (i.e., no drop out of corresponding beacon or other failure)and yield reliable centroid data are used. At least four centroids 234need to be captured from the initial sequenced pattern to measure thevalues of parameters (x, y, z, φ, θ, ψ) in world coordinates (X_(o),Y_(o), Z_(o)) The pose is called absolute when all parameters are knownin global coordinates (X_(o), Y_(o), Z_(o)) at a given time, e.g., att_(init.). Navigation using absolute pose or at least one parameter ofabsolute pose is referred to as absolute tracking or absolutenavigation.

In a particular embodiment, beacons B1, B2, . . . , Bn are positioned ona plane in a rectangular grid pattern and parameters (x, y, z, φ, θ, ψ)are inferred or measured based on projective, i.e., perspectivegeometry. In this approach the rules of perspective geometry using theconcept of vanishing points lying on a horizon line are applied todetermine the location of point of view 214. Specifically, given thelocations of at least four coplanar beacons lying on at least threestraight intersecting lines framing a rectangular grid in the field ofview F.O.V. of lens 210, absolute navigation algorithm 290 defines ahorizon and finds conjugate vanishing points from which point of view214 is determined. Once point of view 214 is known, parameters (x, y, z,φ, θ, ψ) of object 202 are inferred or measured. Initially, point ofview 214 is the origin or reference point at (x, y, z). As mentionedabove, any other point on object 202 can be used as a reference pointbased on a coordinate transformation. The perspective geometry andvector algebra necessary to perform absolute navigation are known toskilled artisans of optical image processing and will not be discussedherein. For more details, the reader is referred to K. Kanatani,“Geometric Computation for Machine Vision”, Oxford Science Publications;Clarendon Press, Oxford; 1993, Chapters 2-3 and to U.S. Pat. No.7,203,384 to Carl.

In embodiments where a large number of beacons are used and areavailable (low drop out), the rules of perspective geometry can beemployed to filter beacons that are non-conformant therewith. In otherwords, the perspective geometry constraint can be used as an additionalfilter for high-precision absolute tracking or navigation.

Absolute pose expressed with inferred or measured values of parameters(x, y, z, φ, θ, ψ) computed by image processing electronics 218 atinitial time t_(init). in step 290 is used to update trajectory 230during pose update step 296. Depending on the motion of object 202 andrequired resolution or accuracy for trajectory 230, the centroid capturerate and time between determinations of absolute pose should beadjusted. At high-speed capture rates absolute navigation algorithm 290can keep updating parameters (x, y, z, φ, θ, ψ) in a continuous fashionbased on at least four most recently captured centroids or even as eachsuccessive centroid is obtained. This can be accomplished bysubstituting the most recently captured centroid for the oldestcentroid. Computed trajectory 230, expressed with absolute poseparameters and time (x, y, z, φ, θ, ψ, t), is output in step 298 to anapplication in the form of a subset. The subset may contain all or fewerthan all of the parameters (x, y, z, φ, θ, ψ, t), depending on therequirements of the application.

The application requires knowledge of object's 202 movements foroperation, feedback, input, control or other functions. The applicationhas a control mechanism that initiates and terminates operation ofmotion capture program via control command 300. In several advantageousapplications object 202 is a hand-held object that is manipulateddirectly by the user and trajectory 230 is used as input for theapplication, as will be addressed in more detail below.

Preferably, upon completion of one cycle of initial sequenced pattern are-evaluation is performed in step 302. During re-evaluation beaconsflagged during step 284 are removed from the data set or the optimizedsequenced pattern to speed up operation. Beacons that fail in filteringor normalization steps 282, 286 may be adjusted or left out as well.Finally, any high quality beacons as determined by tracking ornavigation algorithm 290 can be used for benchmarking or weighting. Ofcourse, these decisions can be periodically re-checked to ensure thatbeacons yielding high quality data at a different pose are not turnedoff permanently. Additionally, intermittent background measurements aremade with all beacons off at regular intervals or on an as-needed basisfor background subtraction.

Alternatively, optimization and re-evaluation of the sequenced patternis performed on-the-fly. In this case the initial cycle does not need tobe completed and information from some beacons, e.g., the latter portionof the cycle may be disregarded altogether.

In a preferred embodiment of the method, the sequenced pattern ofemission of radiation 222 by the beacons is controlled based on the oneor more absolute pose parameters determined by tracking or navigationalgorithm 290. The control can be a temporal control as in when thebeacons are on, or spatial control of which beacons should be usedand/or which beacons should be relocated and affixed at new locations inthe environment. To this effect, in step 304 an optimized sequencedpattern is prepared based on the re-evaluation from step 302. If theapplication issues request 306 for further output from motion captureprogram 270, then the optimized sequenced pattern is activated in step308 and the cycle of centroid capture re-starts at step 278. Otherwise,motion capture program is terminated in step 310.

In an alternative embodiment, motion capture program 270 employs anabsolute navigation algorithm 290 that only determines a subset ofabsolute pose parameters (x, y, z, φ, θ, ψ)

In one example, only (x, y, z) parameters defining the position of pointof view 214 (vector G_(o)) or some other reference point on object 202are determined. These parameters can be used when orientation parameters(φ, θ, ψ) are not required by the application. An example of suchapplication is a three-dimensional digitizer. In another example, onlyorientation parameters (φ, θ, ψ) of the pose of object 202 aredetermined. These can be used by an application that requires onlyorientation or angle information for its input or control functions,e.g., when object 202 is a remote pointer, joystick, three-dimensionalcontroller, pointer, other hand-held object or indeed any object in needof angular tracking or navigation only.

In still another alternative embodiment, motion capture program 270employs a relative navigation algorithm 290′ that only determineschanges in some or all parameters (Δx, Δy, Δz, Δφ, Δθ, Δψ). For example,navigation algorithm 290′ determines linear and/or angular velocities

$\left( {\frac{\mathbb{d}x}{\mathbb{d}t},\frac{\mathbb{d}y}{\mathbb{d}t},\frac{\mathbb{d}z}{\mathbb{d}t},\frac{\mathbb{d}\phi}{\mathbb{d}t},\frac{\mathbb{d}\theta}{\mathbb{d}t},\frac{\mathbb{d}\psi}{\mathbb{d}t}} \right),$accelerations or higher order rates of change, such as jerk, of anyabsolute pose parameter or combinations thereof. It should be noted thatabsolute pose may not be inferred or measured at all by relativenavigation algorithm 290′. Thus, the rates of change may be the resultsof variations of unknown combinations of absolute pose parameters.Relative navigation algorithm 290′ is advantageous for applications thatdo not require knowledge of trajectory 230 but just rates of change.Such applications include navigation of relative hand-held devices suchas two-dimensional mice, three-dimensional mice, relative mouse-pens andother low-accuracy controls or relative input devices.

Apparatus 200 is inherently low-bandwidth, since PSD 212 reports justfour values, namely (x_(i) ⁺, x_(i) ⁻, y_(i) ⁺, y_(i) ⁻) correspondingto the location of centroid 234 produced by one or more known beacons.The intrinsically high signal-to-noise ratio (SNR) of centroid 234 dueto low background noise allows apparatus 200 to operate at high capturerates, e.g., up to 10 kHz and higher, rendering it ideal for trackingfast moving objects. In fact, apparatus 200 is sufficiently robust tonavigate even rapidly moving hand-held objects, including pointers,controllers, mice, high-precision gamer instruments, jotting implementsand the like in close-range environments or constrained areas such asdesks, hand-held notepads, point-of-sale environments and various game-and work-spaces.

Optical navigation apparatus 200 admits of many more specificembodiments. First and foremost, centroid sensing device 212 can usevarious physical principles to obtain the centroid of imageddistribution 232 of electromagnetic radiation 222 (and ambient radiation220). A person skilled in the art will recognize that even a regularfull field sensor, e.g., a digital CMOS sensor, can act as centroidsensing device 212. In general, however, the use of a standardfull-frame capture CMOS sensor with a large number of individual pixelswill not be very efficient. That is due to the large computationalburden associated with processing large numbers of image pixels and lackof intrinsic facility in centroid sensing. In addition, fast motioncapture and high frame rates required for navigating hand-held objectswith on-board optical measuring arrangement are not compatible with thehigh-power and large bandwidth requirements of digital CMOS sensors.

Optical apparatus 200 for processing pose data can employ many othertypes of centroid sensing devices as PSD 212. Some examples of suchdevices can be found in U.S. Patent Application 2007/0211239 to Mandellaet al. A particularly convenient centroid sensing device has circularand planar geometry conformant to the naturally circular F.O.V. of lens210. FIG. 11 shows such a circular PSD 350 of the semiconductor type inwhich the field of view F.O.V. is conformant with a sensing surface 352of PSD 350. In this embodiment four of beacons B1-Bn are active at thesame time and produce an imaged intensity distribution 354 that is aconstellation of four spots 232A, 232B, 232C and 232D at four locationsin the image plane of PSD 350. A center of mass (C.O.M.) ofconstellation 354 at the time of detection is designated with a crossand depends on the relative positions and intensities of spots 232A-D.

The circular geometry of PSD 250 enables operation in polar coordinates(R, θ). In this convention each of four spots 232A, 232B, 232C and 232Dhas a centroid 234A, 234B, 234C and 234D described by polar coordinates(R1, θ1), (R2, θ2), (R3, θ3) and (R4, θ4). However, due to itsprinciples of operation PSD 350 reports to electronics 218 only polarcoordinates (Rc, θc), of the C.O.M.

A set of dashed arrows show the movement of centroids 234A, 234B, 234Cand 234D and C.O.M. as a function of time. Note that applying opticalflow without inferring or measuring the absolute pose of object 202indicates an overall rotation and can be used as input for any relativemotion device, e.g., an optical mouse. In such functional mode, absolutemotion component 208 operates as an auxiliary motion component and moreprecisely an optical flow measuring unit that determines relativemotion. Relative motion information obtained from optical flow can bevery valuable and it can supplement absolute pose data in certain cases.For example, it can be used to interpolate motion of object 202 betweentimes t_(i) when absolute pose is inferred or measured.

In the last step, absolute pose data 248 consisting of all absolute poseparameters (x, y, z, φ, θ, ψ) are transmitted to an application runningon control unit 224 via a wireless communication link 244 using atransceiver 246A on-board object 202 and a transceiver 246B on unit 224.In this embodiment unit 224 is running a monitoring application tosupervise manipulated object 202 without displaying any output.

Note that in this embodiment, electronics 218 can pick the subset thatis needed for the monitoring application running on unit 224. An uplinkexists from unit 224 back to electronics 218 (as indicated) tocommunicate changes in the required subset or subsets for theapplication as they may arise. Thus, if manipulated object 202 is notexperiencing any linear displacements, i.e., the coordinates (x, y, z)of its viewpoint 214 are static, then the subset of orientationparameters (φ, θ, ψ) is not relevant and does not need to be requestedby unit 224.

FIG. 12 illustrates a more application-specific embodiment of anapparatus 400 according to the invention in a real three-dimensionalenvironment 402 defined by a room 404. A manipulated object 406 havingan on-board optical measuring arrangement 408 that has an absolute posemeasuring component 410 is constrained to move within room 404.Component 410 has a lens 412 that is substantially single viewpoint andhas a wide field of view. Component 410 employs a PSD as its sensor (notshown in present figure) in a manner analogous to component 208 of theprevious embodiment.

A series of IR LEDs B1-Bn (not all shown) are located in environment 402at known locations in world coordinates (X_(o), Y_(o), Z_(o)). IR LEDsB1-Bn are distinguishable since they are modulated as beacons in asequenced pattern that is remotely controlled by a computing device 414.Beacons B1-Bn emit light 416 at a fixed wavelength in the infraredrange. Each beacon has a large cone angle 418, as exemplified by beaconB2.

In a manner similar to the previous embodiment, component 410 infers theabsolute pose of manipulated object 406 it terms of measured values ofparameters (x, y, z, φ, θ, ψ) from observing sequentially flashingbeacons B1-Bn. The reference location is the world origin and thereference point on object 406 is its tip 406′.

Absolute pose of object 406 is determined at a rate of 100 Hz or moreand is processed by an on-board processor 407. Processor 407 may be apart of absolute motion measuring component 410 or it can be a separateprocessor. Processor 407 separates absolute pose data 420 into twosubsets P and O. Subset P contains only position parameters (x, y, z) oftip 406′, or equivalently, the components of vector G_(o). Subset Ocontains only orientation parameters (φ, θ, ψ) of object 406. Atrajectory of tip 406′ is designated by P(t), which is the collection ofsubsets P at measurement times t_(i), or P(t)=(x, y, z, t_(i)).Meanwhile a history of orientations of object 406 is designated by O(t),which is the collection of subsets O at measurement times t_(i), orO(t)=(φ, θ, ψ, t_(i)).

Both trajectory P(t) and a representation of orientations O(t) areindicated in dashed lines in FIG. 12. When measurement times t_(i) aresynchronized for both subsets, then subset P and subset O can becombined. Otherwise, they should be kept apart marked with their owncorresponding measurement times t_(i).

A wireless communication link 422 employing a transmitter 424 on object406 and a receiver 426 on computing device 414 is used to transmit posedata 420 to computing device 414. In the present case absolute pose data420 is broken up into time-synchronized subsets P and O. These subsetsare transmitted via link 422 to an application 428 running on computingdevice 414. More specifically, subsets (P,O) captured at times t₁, t₂, .. . t_(i) are transmitted sequentially to application 428 at a rate ofabout 100 Hz or higher.

FIG. 13 illustrates the transmission of subsets 420 and computing device414 receiving subsets 420 in more detail. Computing device 414 has adisplay screen 430 for displaying an output 432 of application 428 to auser (not shown). Note that the user to whom output 432 is displayed onscreen 430 need not be the same user as the one remotely or directlymanipulating object 406. Output 432 is broken down into a number ofvisual elements, including an image 404′ of room 404 and an image 406″of manipulated object 406. Output 432 also includes a graphical paletteof commands and options 434, instructions displayed as text 436 and anicon 438 to launch and terminate application 428.

Subsets 420 a, 420 b, . . . 420 i arriving sequentially viacommunication link 422 provide the input for interacting with output 432of application 428. Application 428 is programmed in such a manner thatprior and newly arrived subsets O and P are represented graphically inthe form of trajectories O(t)′. and P(t)′. In addition, manipulatingobject 406 in real three-dimensional space 402 of room 404 such thatimage 406″ lands on icon 438 turns application 428 on and off.Furthermore, placing image 406″ over commands and options 434 selectsthem. Finally, trajectory P(t)′ can be converted into a digital inktrace and converted into text using standard conversion algorithmsanalogous to those used in tablet PCs and known to those skilled in theart. The converted text can be displayed along text 436 already presenton display screen 430. In this manner, subsets P and O are employed byapplication 428 as input for interacting with its output 432.

Computing device 414 also has a speaker 440 mounted to the side ofdisplay screen 430. Application 428 can thus also take advantage ofaudio elements 442 to supplement output 432 consisting of only visualelements. For example, audio elements 442 can be constituted by tones,e.g., warning tones when image 406″ of object 406 is moving off screen.Another audio element 442 can be a tune, e.g., to announce the launch ortermination of application 428. Still another audio element 442 may be amusical composition that is selected or adjusted in volume or otherauditory parameter by data from subsets P and O. For example, thelocation of tip 406′ as communicated by P(t) can control the volume.Finally, audio element 442 may simply be an alert signal when eithersubset P or O exhibit certain type of data. For example, when trajectoryP(t) changes too rapidly and the user manipulating object 406 in realthree-dimensional space 402 should slow down in moving object 406.

FIG. 14 illustrates yet another embodiment of an apparatus 500 formoving a manipulated object 502 by hand 503 in a real three-dimensionalenvironment 504 while tracking the absolute pose of object 502.Environment 504 is parametrized by world coordinates (X_(o), Y_(o),Z_(o)) World origin (0, 0, 0) is used as the reference location forreporting absolute pose data 506.

On-board optical measuring arrangement 508 has a lens and a PSD in itsabsolute motion detection component. Their arrangement and operation isanalogous to those described in the previous two embodiments. Meanwhile,beacons B1-B4 are IR LEDs mounted on a reference object 510 that ispositioned at a known location and in a known spatial relationship toworld origin (0, 0, 0). In other words, the pose of reference object510, itself parametrized by coordinates (X₁, Y₁, Z₁), as embedded inworld coordinates (X_(o), Y_(o), Z_(o)) is known.

The angular motion or change in orientation parameters of manipulatedobject 502 in environment 504 is expressed with the aid of Euler angles(φ, θ, ψ). The reference point for describing the Euler rotated objectcoordinates is a tool tip 512 of object 502. Position of tool tip 512 isexpressed in Cartesian coordinates (x, y, z). The successive positionsof tool tip 512 are defined with the aid of vectors G_(o) obtained atdifferent times t_(i); i.e., by vectors G_(o)(t_(i)). The actualtrajectory of tool tip 512 is expressed by vectors D_(i) connecting thetips of successive vectors G_(o)(t_(i)). The trajectory of a distal end514 of object 502 is indicated by reference 516.

IR LEDs B1-B4 emit infrared light 518 according to a modulation schemeimposed by a suitable control mechanism (not shown) integrated intoreference object 510. The modulation scheme renders IR LEDs B1-B4distinguishable, as required of light sources serving as beacons. Thenumber of IR LEDs should be increased from the minimum of 4 to at least16 and preferably 32 or more if sub-millimeter accuracy on the absolutepose and absolute motion of object 502 is required. Furthermore, theyshould be spaced as far apart as possible given the dimensions ofreference object 510. For example, a two- or three-dimensional gridpattern is a good spatial arrangement for IR LEDs. Additionally, it isadvantageous if IR LEDs are placed in a grid structure that subtends aportion of environment 504 designated as work space 520 in which tool502 will be operated. For planar arrangements of IR LEDs integrated intoreference object 510, it is also advantageous to operate tool tip 512 asclose as possible to the centroid of the smallest convex set containingthe IR LEDs (i.e., the distribution's convex hull).

When the spatial arrangement and number of IR LEDs is sufficientlyoptimized to yield sub-millimeter accuracy on the location of tool tip512, and sub-degree accuracy on orientation parameters (φ, θ, ψ) withinwork space 520 then object 502 can be a precision tool. For example, inthis embodiment manipulated object 502 can be a jotting implement, asurgical implement, a three-dimensional digitizer, a digitizing stylus,a hand-held tool such as a cutting implement or a utensil. Morespecifically, in the present embodiment tool 502 is a scalpel, workspace 520 is an operating area (patient and incision not shown) and tooltip 512 is a blade tip.

The absolute motion tracking method of the invention with scalpel 502 isimplemented by transmitting pose data 506 via a communication link 522to processor 524 at times t_(i). Processor 524 picks out as subset 526orientation parameters (φ, θ, ψ) and position parameters of tool tip 512described by vectors D_(i) at times t_(i). In order to keep good trackof the sequence of absolute poses, each subset 526 is appended with itscorresponding measurement time t_(i). Thus, subsets 526 are expressed as(φ, θ, ψ, D_(i), t_(i)). Note that vectors D_(i) could alternatively beexpressed in coordinates (X₁, Y₁, Z₁) of reference object 510, since thefull spatial relationship between world coordinates (X_(o), Y_(o),Z_(o)) and reference object 510 is known.

After preparation of absolute pose data 506 and identification ofsubsets 526, processor 524 forwards them to an application 528.Application 528 is preferably implemented on a physician's computer (notshown). Application 528 can be a reality simulation that allows anintern to follow an actual surgery in real time or perform their ownmock surgery with scalpel 502. Application 528 can also be a remotecontrol application, in which a physician performs a surgery with a mockversion of tool 502. Then, a communication link such as the world wideweb 530 relays subsets 526 to another module of remote surgeryapplication 528 that is implemented on a remote device 532 thatduplicates the motion encoded in subsets 526 to perform an actualsurgery on an actual patient at the remote location with an actualscalpel (not shown).

In an alternative embodiment, tool 502 is a hand-held utensil whoseworking tip 512 is used for performing some useful function, e.g.,stamping or marking an object located in work space 520. In this caseapplication 228 is a general motion-capture application and thefrequency of measurement times t_(i) is on the order of 75 Hz. In somemotion-capture applications such as biometric applications requiringprecise knowledge of the motion of utensil 502, e.g., to derive abiometric aspect of hand 503, more frequent measurement times t_(i),e.g., in excess of 100 Hz or event in excess of 200 Hz can be used. Inparticular, such precise knowledge can be required when the biometricapplication is a user verification application.

FIG. 15 is a block diagram illustrating a few exemplary uses of inputderived from a manipulated object that can be used with any of thepreviously embodiments, and especially with the embodiments employingbeacons and PSD sensors. In fact, block diagram may represent a module538 or a routine integrated with any application according to theinvention. For the purposes of the present description, we will show howmodule 538 works with application 528 of the embodiment from FIG. 14.

In a first step 540, subset 526 is received by either a local host or anetwork via communication link 530. If subset 526 is intended for aremote host, then it is forwarded to the remote host in a step 542. In asecond step 544, a processor in the intended host (local host or remotehost, as the case may be) determines the requirements for subset 526.This selection can be made based on an intended final application 546.For example, when final application 546 only requires the parametersalready contained in subset 526, then subset 526 is forwarded to step548 for preparation and direct use. Alternatively, when application 546requires additional parameters, subset 526 is forwarded to step 550 forderivation of these additional parameters.

For example, the additional parameters are derivatives of one or more ofthe parameters in subset 526. Thus, subset 526 is sent to adifferentiation module 552 and then to a preparation module 554 forsupplementing subset 526 with the derivatives. In the example shown,time derivatives of Euler angles ψ and θ are required and thus,supplemented and prepared subset 526′ contains these time derivatives.Alternatively, statistical information about one or more of theparameters in subset 526 are required. Thus, subset 526 is sent to astatistics module 556 and then to a preparation module 558 forsupplementing subset 526 with the statistical information. In thepresent example, the statistical information is a standard deviation ofsecond Euler angle θ. Thus, supplemented and prepared subset 526″contains the parameters of subset 526 and standard deviation σ(θ) ofangle θ.

A person skilled in the art will appreciate that the functions describedcan be shared between local and remote hosts as well as application 546,e.g., as required by the system architecture and data porting standards.For example, some preparation and supplementing of subset 526 can beperformed by application 546 upon receipt.

Subset 526 is transmitted to application 546 for use as an input that istreated or routed according to its use. For example, in a step 560,subset 526′ is used as control data. Thus, subset 526′ is interpreted asan executable command 562 or as a part of an executable command and usedin an executable file 564. On the other hand, in a step 566, subset 526″is used as input data and saved to a data file 568.

In general, application 546 has an output that is presented to one ormore users. Meanwhile, the handling of tool 502 generates subsets 526that are used as input; either in the form of control data or inputdata. There is a feedback loop between motion of tool 502 in realthree-dimensional environment 504 and the output of application 546.Subsets 526 produced from motion of tool 502 by hand 503 in real spaceserve as input for interacting with the output of application 546 thatruns on a computer, e.g., tablet PC 532. This relationship between inputderived from motion of tool 502 in real space and output ofcomputer-implemented application 528 renders the method of inventionideal for interfaces that require a more direct and kinestheticallyintuitive interaction with applications in the digital world. This isparticularly true of applications that include simulations of real worldevents or applications that try to render cyberspace more accessible tohuman users.

FIG. 16 illustrates another alternative embodiment of an apparatus 600according to the invention. In this embodiment manipulated object 602 isa control wand that is to be moved by hand through a realthree-dimensional environment 604. Environment 604 includes a tablet 606whose upper right corner is taken as world origin (0, 0, 0) of worldcoordinates (X_(o), Y_(o), Z_(o)). A tip 602′ of control wand 602 istaken as the reference point for reporting Euler rotated objectcoordinates (X, Y, Z) with respect to world origin (0, 0, 0) in the sameconvention as described above. Similarly, vector D_(o) from world origin(0, 0, 0) to tip 602′ describes the instantaneous location of tip 602′in world coordinates (X_(o), Y_(o), Z_(o)).

Object 602 has an on-board optical measuring arrangement 608 forabsolute pose tracking. Unlike in the prior embodiments, arrangement 608does not rely only on ambient light. Instead, it has an activeillumination component 610. Component 610 includes a source 612 forgenerating a light 614 and optics 616A, 616B for conditioning light 614and projecting it into environment 604. Specifically, optic 616A is abeam splitter and optic 616B is a mirror. Additional optics, such aslenses may be included as well (not shown) for condition and projectinglight 614.

Active illumination component 610 is simultaneously designed to receivea scattered portion 614′ of light 614 coming from one or more invariantfeatures 618A, 618B located in environment 604. In the presentembodiment, features 618A, 618B are markings deposited on the surface oftablet 606. It is particularly advantageous in this embodiment, ifmarkings 618A, 618B are high optical contrast features under projectedlight 614 by virtue of being highly reflective to light 614. In fact,preferably markings 618A, 618B are retro-reflectors or made of aretro-reflective material.

Arrangement 608 employs scattered portion 614′ of light 614 foroptically inferring or measuring the absolute pose of wand 602. Theinferred absolute pose 620 is again reported with parameters (φ, θ, ψ,D_(i), t_(i)), which include the values of vector D_(o) at times t_(i),herein again denoted as D_(i). In order to provide the requisiteinformation in its scattered portion 614′, projected light 614 needs tocarry spatial information. One way to imbue light 614 with suchinformation is to provide it with structure. For example, light 614 canbe a structured light projected in some pattern 622. Pattern 622 can bea time-invariant grid pattern or it can be a time-varying pattern. Theseoptions are well known to those skilled in the art of optical scannerswith constant and time-varying scan patterns.

In the present embodiment, pattern 622 is a time-varying scannedpattern. To accomplish this, active illumination component 610 has ascanning unit 624. Unit 624 drives and controls mirror 616B, which is ascanning mirror in this case. When correctly driven, scanning mirror616B executes an appropriate movement to trace out pattern 622.

In FIG. 16 absolute pose 620 of control wand 602 is indicated with theaid of vector D_(o) and object coordinates (X, Y, Z) rotated three timesby three Euler angles (φ, θ, ψ). Clearly, the manner in which pattern622 imparted on structured light 614 is projected onto or how itintersects invariant features 618A, 618B on the surface of tablet 606will change as a function of the wand's 602 absolute pose 620. It isthis change in projection onto invariant features 618A, 618B thatpermits on-board optical measuring arrangement 608 to infer absolutepose 620 of wand 602. The generation, interpretation and inference ofabsolute pose 620 from appropriate scan patterns and theirback-scattered light is a subject well known in the art and it will notbe discussed herein. For additional teachings on scanning techniques andderivation of pose parameters the reader is referred to U.S. Pat. No.7,023,536 to Zhang et al., U.S. Pat. Nos. 7,088,440; 7,161,664 both toBuermann et al., and the references cited therein.

Scanning mirror 616B may be a tiltable or rotatable mirror, depending onscan pattern 622 desired. In the event mirror 616B is tiltable, it canbe uniaxial for executing a one-dimensional scan pattern 622, or biaxialfor executing a two-dimensional scan pattern 622. A scan point P_(o) ofscan pattern 622 produced with projected light 614 intersecting tablet606 and shown in FIG. 15 is associated with a scan angle σ of scanningmirror 616B.

In the present embodiment, scanning mirror 616B is a tiltable biaxialmirror that executes a two-dimensional scan pattern 622 parametrized byscan angle (a referenced to mirror axis M.A. Additionally, projectedlight 614 is collimated into a scanning light beam 626. Angle δ denotesthe angle of incidence of scanning light beam 626 on tablet 606 at scanpoint P_(o). Angle λ is the inclination angle of wand 602 with respectto the surface of tablet 606. Since invariant features 618A, 618B areretro-reflecting, angle δ is also the angle at which scattered portion614′ returns from them to arrangement 608. A photodetector 628 isprovided on-board wand 602 for receiving scattered portion 614′. Mirror616B and beam splitter 616A guide scattered portion 614′ tophotodetector 628 in this embodiment.

Preferably, the scan of an entire scan pattern 622 is executed rapidly,e.g., at kHz rates. Such rapid scanning is required to generate manyscattered portions 614′ of light 614 coming from retro-reflectinginvariant features 618A, 618B during each second. This ensures thatthere is sufficient data for arrangement 608 to infer absolute pose 620.In addition, scan pattern 622 should cover enough real space to ensurethat scanning light beam 626 intersects features 618A, 618B from any ofthe absolute poses that wand 602 is expected to assume during regularoperation. This can be accomplished by choosing a dense scan pattern 622and a large scan angle σ. One possible two-dimensional scan pattern thatsatisfies these constraints is a Lissajous figure projected over a scanangle σ extending from −35° to +35°.

The times during the scan pattern 622 when scattered portions 614′ aredetected by photodetector 628 indicate where, with respect to wand 602,invariant features 618A, 618B are located at those times. It should benoted that employing scan pattern 622 is also very useful in recognizinginvariant features such as bar codes and other markings extensively usedin commerce. Therefore, wand 602 with active illumination component 610can be particularly useful in applications having to locate andsimultaneously identify bar-code bearing objects that are present inenvironment 604 and may or may not be placed on tablet 606.

FIG. 17 illustrates another embodiment of a manipulated object 700equipped with an active illumination component 702. Object 700 isdesigned to operate in a real three-dimensional environment 704 as astylus whose reference point is its tip 700′. World coordinates (X_(o),Y_(o), Z_(o)) have their origin (0, 0, 0) in the lower left corner of atablet PC 706 with which stylus 700 cooperates as one of its inputdevices. World origin (0, 0, 0) is the reference location with respectto which an absolute pose of stylus 700 is reported in Euler rotatedobject coordinates (x, y, z, φ, θ, ψ).

Active illumination component 702 has a light source, in this caseconsisting of two laser diodes that produce two laser beams. Component702 has two rotating scanning mirrors that produce two planes 708, 710of projected light 712, 714 respectively. Each of these projected planesof light 708, 710 is produced by a respective laser beam, which isscanned within its respective plane by a respective rotating scanningmirror. These types of rotating scanning mirrors are well known to thoseskilled in the art. Preferably, the laser diodes emit in the infrared sothat light 712, 714 is not visible or disruptive to a human user oftablet computer 706. Planes 708, 710 are at right angles to each otherand are perpendicular to a central axis C.A. of stylus 700.

Four reflective elements 716A, 716B, 716C, 716D are mounted on the foursides of a display screen 718 belonging to tablet PC 706. Elements 716have different numbers of retro-reflecting strips 720 that scatter light712, 714 back along the direction from which it arrived. Specifically,element 716A has two retro-reflecting strips 720, element 716B hasthree, element 716C has one and element 716D has four.

Component 702 is one part of an on-board optical measuring arrangement722 of stylus 700. Above component 702, arrangement 722 includes a lens724 and a sensor (not shown) for receiving light portions 712′ and 714′that are back-scattered towards component 702 from environment 704. Asuitable beam splitter, as in the prior embodiment, can be provided inorder to separate back-scattered portions 712′, 714′ of light 712, 714that is being projected into environment 704 in the form of planes 708,710. It is known how to position such a beam splitter such that itdirects back-scattered portions 712′, 714′ to the sensor. Lens 724 hasits field of view (F.O.V.) chosen such that it can receiveback-scattered portions 712′ and 714′, after they have been directed bythe beam splitter and thus image them onto the sensor.

Alternatively, lens 724 can be designed to have a wide-angle panoramicF.O.V. such that it can directly view back-scattered portions 712′, 714′emanating from retro-reflecting strips 720. This alternative designeliminates the need for a beam splitter. In either case, back-scatteredportions 712′, 714′ received at the sensor will comprise a time-sequenceof four back-scattered optical signals as they arrive in the same orderthat the beams are scanned over each of retro-reflecting strips 720. Thetiming of these optical signals can be processed infer the absolute poseof manipulated object 700 in Euler rotated coordinates (x, y, z, φ, θ,ψ) relative to the reference location (0, 0, 0) of tablet PC 706.

During operation, as the two scanning mirrors rotated at a suitableangular velocity, light 712, 714 of planes 708, 710 generates eitherone, two, three or four back scattered portions 712′, 714′. The numberof these back scattered portions 712′, 714′ depends on which of the fourreflective elements 716 is being intersected by planes 708, 710respectively. At the instant shown in FIG. 17, plane 708 intersectsreflective element 716C that has one retro-reflecting strip 720. Hence,one back scattered portion 712′ is produced. Meanwhile, plane 710intersects reflective element 716B with three retro-reflecting strips720 and thus generates three back scattered portions 714′. Thus, thereare produced a total of four back-scattered portions; one 712′ and three714′.

Back-scattered portions 712′, 714′ are rapidly collected by lens 724 andprojected onto the optical sensor. The optical sensor then converts thisrapid sequence of optical signals into electrical signals for furtherprocessing into absolute pose data (x, y, z, φ, θ, ψ). In other words,lens 724 images all scattered portions 712′, 714′ onto the sensor togenerate raw image signals. From these signals and their angulardistribution, arrangement 722 can infer the absolute pose of stylus 700and prepare it in the form of a suitable subset to serve as input fortablet computer 706 in a manner analogous to that explained above.

A person skilled in the art will realize that a large variety of activeillumination components can be implemented in the apparatus ofinvention. However, whether any given optical measuring arrangement hasan absolute motion detection component with a lens and an optical sensoror with an active illumination component or even with both, it is oftenadvantageous to supplement it with an auxiliary motion detectioncomponent. Preferably, such auxiliary motion detection component tracksa relative position or movement and is used for interpolation ofabsolute pose between measurement times t_(i).

FIG. 18 illustrates an embodiment of an apparatus 748 that has a jottingimplement 750 employed with an electronic book reader 752. Reader 752has a display screen 754 with a number of display pixels 756 playing therole of high optical contrast invariant features. Preferably, displayscreen 754 in this embodiment is an OLED device and designated displaypixels 756 emit light 758 in the infrared range of the electromagneticspectrum so as not to interfere with a user's visual experience. Inaddition screen 754 is a touch sensitive screen that allows a user tomanipulate visual elements by touch or multi-touch gestures.

Implement 750 has an on-board optical measuring component 760 with alens that images its field of view onto a photosensor (not shown).Component 760 uses pixels 756 as beacons. For this reasons, theprocessor of reader 752 modulates pixels 756 in a known pattern. At thetime shown, only pixel 756′ is emitting light 758.

With the aid of pixels 756 acting as distinguishable light sources orbeacons, the absolute pose of implement 750 is optically inferred bycomponent 760. Nib 750′ of implement 750 is selected as the referencepoint. The absolute pose is expressed as absolute pose data in worldcoordinates (X_(o), Y_(o), Z_(o)) with respect to world origin (0, 0,0). As before, the absolute pose data are in the form of Euler rotatedobject coordinates (x, y, z, φ, θ, ψ) or their equivalent. Depending onthe application, the processor of reader 752 identifies among parameters(x, y, z, φ, θ, ψ) the subset that will serve as input to theapplication running on reader 752. For example, only (x, y) parametersin the plane of display screen 754 are employed if the input is torepresent digital ink.

Implement 750 also has an auxiliary component 762 mounted on-board.Component 762 is an inertial sensing device such as a gyroscope oraccelerometer. The principle of operation of these relative motiondevices relies on detecting or integrating changes in motion. Whileundergoing these changes, such devices may take into account theconstant presence of the gravitational field g in the Earth's frame ofreference (X^(i), W^(i), Z^(i)) In addition, may be subject to spuriousmeasurements in accelerating frames of reference, such as in a car or onan airplane. For this reason, inertial devices are not suitable fordetermining the absolute pose of implement 750. However, over shortperiods of time, e.g., between times t_(i) when absolute pose isinferred optically by component 760, these devices can detect relativechanges in pose.

In cases where it may be required to minimize the computational load ofthe on-board absolute motion detection component 760 by collectingabsolute pose data (x, y, z, φ, θ, ψ) at a slower rate, then it may beadvantageous to use such inertial devices for interpolation of themotion between times t_(i). The combining of absolute and relativetracking data is sometimes referred to as “sensor fusion” and is basedon techniques that are well known in the art of robotics. For moregeneral information about inertial sensors, the reader is referred tothe product manuals for inertial systems produced by CrossbowTechnology, Inc.

In an alternative apparatus 800 shown in FIG. 19, a hand-heldmanipulated object 802 has an on-board optical measuring arrangement 804for optically inferring the absolute pose of object 802 in a realthree-dimensional environment 806. The absolute pose is expressed withabsolute pose data (x, y, z, φ, θ, ψ) in world coordinates (X_(o),Y_(o), Z_(o)) with respect to world origin (0, 0, 0). Tip 802′ of object802 is the reference point for the Euler rotated object coordinates. Anyof the arrangements taught above can be used in conjunction with anytypes of invariant features to infer the absolute pose. These elementsare not shown in this embodiment for reasons of clarity.

Arrangement 804 infers the absolute pose of object 802 at measurementtimes t_(i). It sends the corresponding absolute pose data (x, y, z, φ,θ, ψ) via a communication link 803 to a processor 805. For bettervisualization, times t_(i) when absolute pose is inferred correspond totip 802′ locations indicated by points 801. Then, as in the priorembodiments, processor 805 identifies the necessary subset or subsetsand provides them to an application 807 for use as input.

Object 802 has an auxiliary motion detection component 808 in the formof an optical flow measuring unit. Unit 808 has an emitter 810 foremitting a light 812 and a detector 814 for measuring scattered light812′. During operation, scattered light 812′ returning from a scatteringpoint 816 on a surface, or else from miniature scattering centersprovides a relative measure of change in pose.

Unit 808 will be familiar to those skilled in the art and is analogousto those used by an optical flying mouse or a regular optical mouse, iftip 802′ is maintained near a scattering surface. In the case of anoptical flying mouse, the image flow data is derived from the movingimages of distant microscopic 3-D objects that are imaged onto a CCDcamera sensor playing the function of detector 814. The informationgained by this type of motion is used to track primarily only therelative angular motion of the mouse with respect to the 3-D environmentcontaining the distant objects. In the case where component 808 is thatof an ordinary optical mouse, the image flow data is derived from themoving images of microscopic features 811 on a surface 813 that object802 is moving over, as shown in the present embodiment. Features 811 areimaged up close and magnified onto CCD camera 814, and the informationgained by this method allows relative tracking of primarily only thetranslational motion of the mouse with respect to surface 813 containingfeatures 811.

In both cases, the relative tracking data can be in the form of angularor linear velocities. These data can be integrated to give points alonga relative path of motion and used for used for interpolation betweentimes t_(i) when absolute pose data is found. Thus, as absolute data isused to define an absolute motion of hand-held manipulated object 802 ata certain resolution dictated by times t_(i), relative data is used tofill in relative motion information between times t_(i).

A person skilled in the art will realize that the absolute motiondetection arrangements of the invention can itself be operated in arelative capture mode in addition to operating in the absolute motioncapture or tracking mode. In other words, they can also double asauxiliary motion detection modules that provide relative motioninformation in some embodiments.

FIG. 20A illustrates another apparatus 840 operated in a realthree-dimensional environment 842. Apparatus optically infers theabsolute pose of a manipulated object 844 with the aid of an on-boardoptical measuring arrangement 846 and suitable invariant features 848 inenvironment 842. At time t_(i) shown in the figure, feature 848′ isemitting a light 850.

Environment 842 is of the kind in which there exists a stationarymagnetic field B, here indicated by a corresponding vector. This type ofenvironment 842 is found, for example, on the surface of the Earth.Apparatus 840 has an auxiliary motion detection component 852 that isrepresented by an electronic magnetic sensing component. Component 852is located in the body of manipulated object 844 for sensing changes inrotation of object 844 with respect to the magnetic field linesestablished by field B. Such changes produce a signal that representsthe relative rotational velocity of manipulated object 844. Theserelative rotational velocities can be used for interpolation betweentimes t_(i), or when absolute pose is not being measured by arrangement846.

FIG. 20B illustrates same apparatus 840, but with a different on-boardauxiliary motion detection component 854. Component 854 is an acousticsensor and it works in conjunction with a number of acoustic sources 856located in three-dimensional environment 842. Sources 856 emit acousticsignals 858. Component 854 measures relative motion of object 804between measurement times t_(i) based on the measurement of the relativeDoppler frequency shifts of acoustic signals 858 emanating from acousticsources 856. A person skilled in the art will be familiar with theoperation of acoustic systems with requisite performance features. Infact, a skilled artisan will recognize that the present absolute poseinferring apparatus and method can be advantageously combined with anysingle or multiple auxiliary motion detection components that determinerelative motion or position and hence provide data useful forinterpolation or cross-checking of absolute pose data.

The various embodiments of apparatus and methods of the invention foroptically inferring absolute pose from on-board a manipulated object andreporting absolute pose data in a priori established world coordinatesis useful for many applications. In particular, any application forwhich actions or movements of the manipulated object in realthree-dimensional environment yields useful input stands to benefit fromthe apparatus and method. Such application may involve a simulation inwhich real environments are reproduced in a cyberspace or in a virtualspace used by the application as part of its output.

FIG. 21 illustrates an application 880 that is a cyber game. A user orplayer 882 (only right arm shown) interacts with application 880 bymoving a manipulated object 884, in this case a tennis racket in a realthree-dimensional environment 886. Racket 884 is a game control ratherthan an actual tennis racket. According to the invention, racket 884 hasan on-board optical measuring arrangement 888 that infers the absolutepose of racket 884. Arrangement 888 performs this task by viewingtemporally modulated beacons B1-B7, B9 disposed on a frame 892 around adisplay screen 890 and a screen pixel B8, also used as a beacon.Preferably, all beacons B1-B9 emit electromagnetic radiation or light893 in the infrared portion of the spectrum.

Conveniently, environment 886 is parametrized by a Cartesian coordinatesystem (X_(o), Y_(o), Z_(o)) whose origin (0, 0, 0) is set at the lowerright corner of frame 892. This Cartesian coordinate system serves asthe world coordinates for application 880 and for arrangement 888. Inaddition, origin (0, 0, 0) is selected as the reference location withrespect to which absolute poses of racket 884 will be opticallyinferred.

A computing device 894 that runs game 880 employs screen 890 forpresenting an output 896 to user 882. Computing device 894 can be apersonal computer, a dedicated gaming computer, a portable computer, atelevision system, any general computing device, hosting network orcomputing platform with sufficient resources to run game 880 on screen890. In the present case, game 880 is a cyber game of tennis, and thusoutput 896 includes visual elements 898 necessary to represent a tenniscourt and a tennis match. Elements 898 include a tennis net 898A, atennis ball 898B, an adversary with a tennis racket 898C, a court 898Dand a replica or image 884′ of racket 884 held by user 882 playing game880. In addition, an avatar 900 representing user 882 is added to output896. It is avatar 900 that is shown holding a token of the racket; inthis particular case it is just replica 884′ of racket 884.

Output 896 is in fact a cyberspace in which tennis game 880 unfolds andin which its elements 898, racket replica 884′ and avatar 900 arerepresented. Cyberspace 896 does not need to be parametrized like realthree-dimensional environment 886. However, to provide user 882 with arealistic game experience, it is preferable that cyberspace 896 bear ahigh degree of correspondence to real space. For that reason, cyberspace896 is parameterized with three-dimensional Cartesian coordinates (X₁,X₂, X₃) that are at least loosely related to world coordinates (X_(o),Y_(o), Z_(o)) In the most realistic scenarios, game 880 can even use aone-to-one mapping of cyberspace 896 to real space 886.

Racket 884 has a reference point 902, which is in the center of its faceand corresponds to the “sweet spot” of a normal tennis racket. Unlikethe previous embodiments, reference point 902 is not an actual point onmanipulated object 884 but a point that is defined in a clear relationthereto. Nonetheless, reference point 902 is used for reporting absolutepose data (x, y, z, φ, θ, ψ) inferred at measurement times t_(i) byarrangement 888.

Racket 884 is also provided with an auxiliary motion detection component904. In this embodiment, component 904 is an inertial sensing device.This specific device has a three-axis accelerometer 906 and a three-axisgyroscope 908. Between measurement times t_(i), gyroscope 908 providesinformation about changes in the orientation. This information can berepresented by some or all Euler angles (φ, θ, ψ), any subset orcombination thereof, some other angular description of orientationchanges including concepts such as pan angles and changes therein.Meanwhile, also between measurement times t_(i), accelerometer 906provides information about linear displacements that can be expressed inparameters (x, y, z), their subset, some combination thereof or stillanother description of linear displacement.

The combination of the subset or subsets from absolute pose data (x, y,z, φ, θ, ψ) and relative motion data are used by tennis game 880 asinput for interacting with output 896. Specifically, the visual elements898B, 898C as well as avatar 900 and replica 884′ of racket 884 aremodified and re-arranged as a function of the input in accordance withthe rules of the game of tennis implemented by the software programmingof game 880. Thus, visual element 898B representing the ball bouncesfrom replica 884′ as the latter is “swung” in cyberspace 896 to hit gallelement 898B. When “hit” correctly, ball element 898B flies to the sideof court 898D of adversary 898C. Meanwhile, avatar 900 follows thepresumed motion of player 882 in real three-dimensional environment 886.The input does not re-arrange or modify court element 898D, since thatpart of the game is a stationary part of cyberspace 896.

A person skilled in the art will recognize that with minor modificationsto cyberspace 896, game 880 could be a squash match where game object884 is a squash racket. Game 880 could also be a golf game in which gameobject 884 is a golf club, or a baseball game in which game object 884is a bat. Similar modifications can be made to implement games incyberspace 896 in which game object 884 is a club, a bowling ball, aknife, a sword, a spear, a joystick, a steering wheel or a flyingcontrol. It should also be noted, that replica 884′ could be a differentvisual element or a token that does not even correspond in appearance tothe physical appearance of game object 884. In this manner, a generallyelongate game object 884 could be represented by suitable token 884′within game 880. Such token would not be an image or a replica of gameobject 884 but, rather, the appropriate game object required by game880. It is especially useful, when implementing game 880 to perform tomake gamer 882 feel like they are performing moves with game objects 884better than in real life, as this type of ego stroking will promote moreusage.

FIG. 22 illustrates another apparatus 918 according to the invention, inwhich a manipulated object 920 is an aircraft being remotely controlledor thrown by a user (not shown) in real three-dimensional space orenvironment 922. Aircraft 920 has an on-board optical measuringarrangement 924 of the type that determines the absolute pose ofaircraft 920 with a single absolute pose measuring component that has alens and a PSD. Although no auxiliary motion detection component formeasuring relative changes in pose parameters is shown, it will beapparent to a person skilled in the art that one or more such componentscould be used.

Invariant features in this embodiment are two sets of temporallymodulated IR LEDs acting as beacons, namely: 926A-D and 928A-D. Beacons926A-D are mounted on a remote control 930, and more precisely on aflying control. Beacons 928A-D are mounted around a landing strip 932.Beacons 928A-C may emit light 929 at a different wavelength λ than thatof light 927 emitted by beacons 926A-D. This makes it easier todifferentiate beacons that are stationary in environment 922 from thosethat are moving (on flying control 930).

A computer 934 remotely controls the modulations of all beacons 926A-D,928A-D and also receives absolute pose data 936 from arrangement 924 viaa wireless communication link 938. The processor of computer 934determines which of absolute pose data 936 to include the subsets to beused by a flying application 940 running on computer 934.

Flying application 940 requires one-to-one mapping between realthree-dimensional environment 922 and its cyberspace. For this reason,world coordinates (X_(o), Y_(o), Z_(o)) with a reference location attheir origin that is coincident with a corner of landing strip 932 arechosen as global coordinates. The reference point on aircraft 920 forreporting absolute pose data 936 in Euler rotated object coordinates (X,Y, Z)—shown with all three rotations in the upper right corner for easyreference—is its center of mass (C.O.M).

Meanwhile, flying control 930 defines an auxiliary reference coordinatesystem (X_(r), Y_(r), Z_(r)) with its origin at the lower right-handcorner of control 930. At each measurement time t_(i), computer 934computes the relative pose of control 930 in global coordinates (X_(o),Y_(o), Z_(o)). This relative information is made available toarrangement 924 via link 938. Thus, arrangement 924 has all therequisite information about the instantaneous locations of all beacons926, 928. This enables it to optically infer its absolute pose atmeasurement times t_(i). In addition, the pose of flying control 930 canbe used to remotely control the flying behavior of aircraft 920. Forexample, the pose in which flying control 930 is held, corresponds tothe pose that the user is instructing aircraft 920 to assume next. Themechanisms for aircraft control to implement such command are well knownand will not be discussed herein.

Application 940 may keep track of the orientation O(t) and position P(t)of the center or mass (C.O.M.) of aircraft 920. It may further displaythis information in a visual form to the user on its display 942. Forexample, it may display O(t) and P(t) at the various times during flightin the form of a view from the cockpit. Such display may serve forflight simulation programs, training purposes or military drills. Inaddition, audio output, such as danger signals or tones can be emittedwhen O(t) and P(t) indicate an impending stall situation based on theapplication of standard avionics algorithms.

Yet another apparatus 950 supporting two manipulated objects 952A, 952Bin a real three-dimensional environment 954 according to the inventionis illustrated in FIG. 23. Objects 952A, 952B are equipped with theiron-board optical measuring arrangements 956A, 956B that use lenses andPSDs to infer their absolute poses from viewing beacons 958. A 3-Dreference object 960 supports a number of beacons 958 disposed in a 3-Dgrid pattern thereon. A wired link 962 connects object 960 to a computer964.

Computer 964 defines world coordinates (X_(o), Y_(o), Z_(o)) having anorigin coinciding with its lower left corner. These are the globalcoordinates for reporting absolute pose data of both objects 952A, 952B.Computer 964 also controls the modulation pattern of beacons 958 vialink 962. Furthermore, it sends corresponding information about the fulllocation (absolute pose) of object 960 with its beacons 958 in worldcoordinates (X_(o), Y_(o), Z_(o)) to arrangements 956A, 956B viacorresponding wireless communication links 966A, 966B. Thus,arrangements 956A, 956B are appraised of the location and modulation ofbeacons 958 at all measurement times t_(i) to permit absolute motioncapture or tracking of objects 952A, 952B.

Object 952A is a gun, a laser shooter, a general projectile launcher oranother war object or implement. War object 952A is handled by amilitary trainee 968 in the conventional manner. The reference point ofwar object 952A corresponds to the center of the outlet of itsprojectile launching nozzle. The coordinates defining the Euler rotatedobject coordinates (X₁, Y₁, Z₁) of object 952A are shown on the nozzlewith direction X₁ being collinear with a projectile direction PD. Theorigin of these object coordinates (X₁, Y₁, Z₁) is described by vectorG₁ in world coordinates (X_(o), Y_(o), Z_(o)).

Object 952B is a wearable article, in this case a pair of glasses wornby military trainee 968. The reference point of object 952B is not apoint on object 952B, but rather an estimated position of the center ofthe trainee's head. Thus, the orientation portion (φ, θ, ψ) of theabsolute pose of object 952B as optically inferred by arrangement 956Bis also an indication of the attitude of the trainee's head.Specifically, trainee's looking direction LD can thus be automaticallyinferred and tracked. The Euler rotated object coordinates (X₂, Y₂, Z₂)of object 952B are thus drawn centered on the trainee's head anddescribed by vector G₂ in world coordinates (X_(o), Y_(o), Z_(o)).

A virtual reality simulation program 970, which is a military drill runson computer 964. Program 970 displays the combat scenario in a virtualreality 972 on a projected display 974 to help monitor the progress oftrainee 968. Scenario is constructed in cyberspace with output thatincludes visual elements 976, 978, 980. Elements 976, 978, 980correspond to two virtual enemy combatants and a virtual projectile.Also, the projectile direction PD′ and looking direction LD′ arevisualized. An avatar 968′ corresponding to trainee 968 is located invirtual reality 972 and is displayed on projected display 974 formonitoring purposes.

Preferably, trainee 968 is provided with the same visual elements ofvirtual reality 972 as shown on display 974 via a virtual retinaldisplay or a display integrated with glasses 952B. This way, trainee cantest his war skills on enemy combatants 976, 978. However, forpedagogical reasons, avatar 968′ is not displayed to trainee 968. Directdisplay technologies are well known to those skilled in the art ofvirtual reality or augmented reality.

During operation, arrangements 956A, 956B infer their absolute poses inenvironment 954 and transmit the corresponding absolute pose data tocomputer 964. The computer uses a subset of the data to enact the warexercise. Note that because objects 952A, 952B report their absolutepose data separately, they can be decoupled in virtual reality program970. This is advantageous, because it allows to simulate a morerealistic scenario in which trainee 968 can point and shoot gun 952A ina direction PD that is different from where he or she is looking, i.e.,direction LD. In fact, in the present situation this behavior isrequired in order to deal with two virtual combatants 976, 978simultaneously.

A person skilled in the art will realize that the application will beimportant in dictating the appropriate selection of manipulated objector objects. In principle, however, there is no limitation on what kindof object can be outfitted with an on-board optical arrangement forinferring its absolute pose with respect to a reference location inglobal coordinates parameterizing any given real three-dimensionalenvironment. Of course, many applications that simulate the real worldand many gaming applications, virtual reality simulations and augmentedreality in particular, may request subsets that include all absolutepose data (φ, θ, ψ, x, y, z). This request may be necessary to performone-to-one mapping between space and the cyberspace or virtual spaceemployed by the application.

Whether fully virtual or not, applications typically provide the userwith output of some variety. Normally, a rather small subset of absolutepose data can allow the user to interact with the output. For example,the supported interaction may include text input, which only requires atrace or re-arrangement of the output. In another case, it may onlyrequire a subset of one translational parameter to move or re-arrangesome visual elements of the output. Given that the output may includeaudio elements and visual elements, the interaction applies to either orboth of these types of output elements at the same time or sequentially.Since in many cases not all of the absolute pose data is necessary tointeract with the output, the remainder of the absolute pose data can beused for still other purposes. For example, a certain absolute motionsequence executed with the manipulated object can be reserved forcommands outside the application itself, such as dimming the display,adjusting display brightness, rotating or touching-up visual elements oreven turning the computer running the application on and off.

Some augmented reality applications may further superpose one or morevirtual elements onto the real three-dimensional environment. Thevirtual element or elements can be then rendered interactive with themanipulated object by the application.

This situation is illustrated in FIG. 24, where an augmented realityapplication 990 shows on a display 992 of a mobile device 994 an imageof real three-dimensional environment 996. To do this, device 994 isequipped with a camera module.

Mobile device 994 is simultaneously a manipulated object in the sense ofthe present invention. Thus, device 994 has an on-board opticalmeasurement arrangement 998 for inferring its absolute pose at timest_(i) with respect to environment 996. The coordinate systems, referencelocation and reference point on object 994 are not shown in this drawingfor reasons of clarity. Also, in this case the invariant features usedby arrangement 998 are not light sources but, rather, are known objectsin environment 996, including house 1000, road 1002 and other featuresthat preferably have a high optical contrast and are easy forarrangement 998 to detect.

Augmented reality application 990 displays not only an image ofenvironment 998, but also has a virtual element 1004. In the presentcase, element 1004 is a description of services provided in house 1000at which device 994 is pointed. Element 1004 is superposed on the imageof environment 996 at an appropriate position to make it easily legibleto the user.

A person skilled in the art will appreciate that the Euler conventionused to report absolute pose data is merely a matter of mathematicalconvention. In fact, many alternative parameterization conventions thatare reducible to the Euler parameters or subsets of the Euler parameterscan be employed.

It should further be noted that the manipulated object can be any typeof device whose absolute pose can yield useful data. Thus, although theabove examples indicate a number of possible manipulated objects othertypes of objects can be used. Also, the subset identified from theabsolute pose data can be supplemented with various additional data thatmay be derived from other devices that are or are not on-board themanipulated object. For example, pressure sensors can indicate contactof the manipulated device with entities in the real three-dimensionalenvironment. Other sensors can be used to indicate proximity or certainrelative position of the manipulated object with respect to theseentities. Furthermore, the absolute pose data and/or supplemental datain the subset can be encrypted for user protection or other reasons, asnecessary.

It will be evident to a person skilled in the art that the presentinvention admits of various other embodiments. Therefore, its scopeshould be judged by the claims and their legal equivalents.

1. An apparatus for processing absolute pose data derived from anabsolute pose of a manipulated object in a real three-dimensionalenvironment, said apparatus comprising: a) at least one invariantfeature in said real three-dimensional environment; b) an opticalmeasuring means for optically inferring said absolute pose from on-boardsaid manipulated object using said at least one invariant feature andexpressing said inferred absolute pose with absolute pose data (φ, θ, ψ,x, y, z) representing Euler rotated object coordinates expressed inworld coordinates (X_(o), Y_(o), Z_(o)) with respect to a referencelocation; c) a processor for preparing said absolute pose data andidentifying a subset of said absolute pose data; and d) a communicationlink for transmitting said subset to an application.
 2. The apparatus ofclaim 1, wherein said reference location is a world origin (0, 0, 0) ofsaid world coordinates (X_(o), Y_(o), Z_(o)).
 3. The apparatus of claim1, wherein said at least one invariant feature comprises at least onehigh optical contrast feature.
 4. The apparatus of claim 3, wherein saidat least one high optical contrast feature comprises at least onepredetermined light source.
 5. The apparatus of claim 4, wherein said atleast one predetermined light source is selected from the groupconsisting of screens, display pixels, fiber optical waveguides andlight-emitting diodes.
 6. The apparatus of claim 5, wherein saidlight-emitting diode is an infrared emitting diode.
 7. The apparatus ofclaim 3, wherein said at least one high optical contrast featurecomprises a retro-reflector.
 8. The apparatus of claim 1, wherein saidapplication comprises an output displayed to a user and said subsetcomprises input for interacting with said output.
 9. The apparatus ofclaim 8, wherein said output comprises at least one visual element. 10.The apparatus of claim 9, wherein said at least one visual element isselected from the group consisting of images, graphics, text and icons.11. The apparatus of claim 9, further comprising a display fordisplaying said visual elements.
 12. The apparatus of claim 11, whereinsaid display comprises a touch sensitive display.
 13. The apparatus ofclaim 8, wherein said output comprises audio elements.
 14. The apparatusof claim 13, wherein said audio elements are selected from the groupconsisting of tones, tunes, musical compositions and alert signals. 15.The apparatus of claim 13, further comprising a speaker for playing saidaudio elements.
 16. The apparatus of claim 1, wherein said opticalmeasuring means comprises a light-measuring component having a lens andan optical sensor.
 17. The apparatus of claim 16, wherein said opticalsensor is a photodetector for sensing light from said at least oneinvariant feature.
 18. The apparatus of claim 17, wherein said at leastone invariant feature comprises at least one predetermined light sourceand said photodetector is a position-sensing device for determining acentroid of light flux from said at least one predetermined lightsource.
 19. The apparatus of claim 18, wherein said at least onepredetermined light source comprises a plurality of infrared emittingdiodes.
 20. The apparatus of claim 19, wherein said plurality ofinfrared emitting diodes is modulated in a predetermined modulationpattern.
 21. The apparatus of claim 1, wherein said optical measuringmeans comprises an active illumination component for projecting apredetermined light into said real three-dimensional environment and forreceiving a scattered portion of said predetermined light from said atleast one invariant feature.
 22. The apparatus of claim 21, wherein saidactive illumination component comprises a scanning unit having ascanning mirror for directing said predetermined light into said realthree-dimensional environment.
 23. The apparatus of claim 1, furthercomprising an auxiliary motion detection component.
 24. The apparatus ofclaim 23, wherein said auxiliary motion detection component is aninertial sensing device.
 25. The apparatus of claim 24, wherein saidinertial sensing device is selected from the group consisting ofgyroscopes and accelerometers.
 26. The apparatus of claim 23, whereinsaid auxiliary motion detection component is selected from the groupconsisting of an optical flow measuring unit, a magnetic field measuringunit and an acoustic field measuring unit.
 27. The apparatus of claim 1,wherein said manipulated object is selected from the group consisting ofpointers, wands, remote controls, three-dimensional mice, game controls,gaming objects, jotting implements, surgical implements,three-dimensional digitizers, digitizing styluses, hand-held tools andutensils.
 28. The apparatus of claim 27, wherein said gaming objects areselected from the group consisting of golfing clubs, tennis rackets,squash rackets, guitars, guns, knives, swords, spears, balls, clubs,bats, steering wheels, joysticks and flying controls.
 29. The apparatusof claim 1, wherein said application is selected from the groupconsisting of reality simulations, remote control applications, cybergames, virtual worlds, searches, photography applications, audioapplications and augmented realities.
 30. A method for processingabsolute pose data derived from an absolute pose of a manipulatedobject, said method comprising: a) placing said manipulated object in areal three-dimensional environment with at least one invariant feature;b) optically inferring said absolute pose from on-board said manipulatedobject using said at least one invariant feature and expressing saidinferred absolute pose with absolute pose data (φ, θ, Ψ, x, y, z)representing Euler rotated object coordinates expressed in worldcoordinates (X_(o), Y_(o), Z_(o)) with respect to a reference location;c) preparing said absolute pose data using a processor; d) identifying asubset of said absolute pose data; and e) transmitting said subset to anapplication using a communication link.
 31. The method of claim 30,wherein said manipulated object is undergoing a motion and said opticalinferring is performed periodically at times t_(i), such that saidabsolute pose data describes said motion.
 32. The method of claim 30,wherein said at least one invariant feature comprises at least onepredetermined light source and said method comprises modulating said atleast one predetermined light source.
 33. The method of claim 30,wherein said subset comprises at least one orientation parameter. 34.The method of claim 33, wherein said at least one orientation parametercomprises at least one Euler angle.
 35. The method of claim 30, whereinsaid subset comprises at least one position parameter.
 36. The method ofclaim 35, wherein said at least one position parameter comprises atleast one Cartesian coordinate.
 37. The method of claim 30, wherein saidsubset comprises all absolute pose data (φ, θ, ψ, x, y, z) and saidapplication comprises one-to-one motion mapping between said realthree-dimensional space and a cyberspace of said application.
 38. Themethod of claim 30, wherein said application provides an output and saidsubset is used for a user interaction selected from the group consistingof text input, modification of said output, re-arrangement of saidoutput.
 39. The method of claim 38, wherein said output comprises atleast one element selected from the group consisting of audio elementsand visual elements.
 40. The method of claim 30, wherein said step ofoptically inferring comprises receiving light from said at least oneinvariant feature by an optical measuring component having an opticalsensor and a lens.
 41. The method of claim 30, wherein said step ofoptically inferring comprises projecting a predetermined light into saidreal three-dimensional environment containing said at least oneinvariant feature and receiving a scattered portion of saidpredetermined light beam from said at least one invariant feature. 42.The method of claim 41, wherein said step of projecting furthercomprises directing said predetermined light into said realthree-dimensional environment by scanning.
 43. The method of claim 30,further comprising interpolating said absolute pose with an auxiliarymotion detection component.
 44. The method of claim 43, wherein saidauxiliary motion detection component comprises an inertial sensingdevice and said step of interpolating is performed when not opticallyinferring said absolute pose.
 45. The method of claim 43, wherein saidauxiliary motion detection component is selected from the groupconsisting of optical flow measuring units, magnetic field measuringunits and acoustic field measuring units, and said step of interpolatingis performed when not optically inferring said absolute pose.
 46. Themethod of claim 30, wherein said application comprises representing auser by an avatar having a token corresponding to said manipulatedobject.
 47. The method of claim 30, wherein said application superposesat least one virtual element onto said real three-dimensionalenvironment.
 48. The method of claim 47, wherein said at least onevirtual element is rendered interactive with said manipulated object bysaid application.
 49. The method of claim 47, wherein said virtualelement comprises data about at least one aspect of said realthree-dimensional environment.